<B>tetherball, </B>noun.<DL COMPACT><DD><B> 1. </B>a game played by two persons with a ball fastened by a cord to the top of a tall post. The object of each person is to hit the ball so as to wind the cord around the post, in one direction or the other. <DD><B> 2. </B>the ball used in this game. </DL>
<A NAME="tethyan">
<B>Tethyan, </B>adjective.<DL COMPACT><DD> (Geology.) of or having to do with Tethys. <BR> <I>Ex. the Tethyan system of ocean trenches.</I> </DL>
<A NAME="tethys">
<B>Tethys, </B>noun.<DL COMPACT><DD><B> 1. </B>(Greek Mythology.) the wife of Oceanus, daughter of Uranus and Gaea. <DD><B> 2. </B>(Geology.) a large triangular sea that hypothetically separated Africa and Eurasia before the drifting of continents. <BR> <I>Ex. Long before the existence of the present Mediterranean, perhaps a quarter of a billion years ago, a giant waterway, the Tethys, extended across southern Europe, Iran and southern China to the Pacific Ocean. The Mediterranean is generally considered to be a remnant of the Tethys (Science News).</I> <DD><B> 3. </B>a satellite of Saturn. </DL>
<A NAME="teton">
<B>Teton, </B>noun, pl. <B>-ton</B> or <B>-tons.</B><DL COMPACT><DD><B> 1. </B>a member of the western division of the Sioux Indians. The best-known tribe of this division was the Oglala. <DD><B> 2. </B>the language of this group, forming a dialect of Dakota. </DL>
<A NAME="tetr">
<B>tetr-,</B><DL COMPACT><DD> (combining form.) the form of <B>tetra-</B> sometimes before vowels, as in <I>tetrarch.</I> </DL>
<A NAME="tetra">
<B>tetra, </B>noun.<DL COMPACT><DD> any one of a group of small, brilliantly colored fishes of the upper Amazon region, such as the neon tetra and flame tetra. </DL>
<A NAME="tetra">
<B>tetra-,</B><DL COMPACT><DD> (combining form) four, as in <I>tetrachloride, tetravalent.</I> Also, sometimes <B>tetr-</B> before vowels. </DL>
<A NAME="tetrabasic">
<B>tetrabasic, </B>adjective.<DL COMPACT><DD> (Chemistry.) <DD><B> 1. </B>(of an acid) having four hydrogen atoms that can be replaced by basic atoms or radicals. <DD><B> 2. </B>having four atoms or radicals of a univalent metal. <DD><B> 3. </B>containing four basic hydroxyl (-OH) radicals. </DL>
<A NAME="tetrabranchiate">
<B>tetrabranchiate, </B>adjective, noun.<DL COMPACT><DD><I>adj. </I> of or belonging to an order of cephalopods that have two pairs of gills and an external shell, as the pearly nautilus and certain fossil mollusks. <DD><I>noun </I> a tetrabranchiate cephalopod. </DL>
<A NAME="tetracainehydrochloride">
<B>tetracaine hydrochloride,</B><DL COMPACT><DD> a drug used as a local anesthetic in the eye, nose, throat, and spinal canal; Pontocaine. </DL>
<A NAME="tetrachloride">
<B>tetrachloride, </B>noun.<DL COMPACT><DD> a compound containing four atoms of chlorine combined with another element or radical. </DL>
<B>tetrachord, </B>noun.<DL COMPACT><DD> (Music.) <DD><B> 1. </B>a diatonic scale series of four notes, the first and last being a perfect fourth apart (the most important unit of Greek melody and music theory); half an octave. <DD><B> 2. </B>an ancient instrument with four strings. </DL>
<A NAME="tetrachordal">
<B>tetrachordal, </B>adjective.<DL COMPACT><DD> having to do with a tetrachord; consisting of tetrachords. </DL>
<A NAME="tetrachotomous">
<B>tetrachotomous, </B>adjective.<DL COMPACT><DD><B> 1. </B>divided or dividing into four parts. <DD><B> 2. </B>branching into four parts; giving off shoots by fours. </DL>
<A NAME="tetrachotomy">
<B>tetrachotomy, </B>noun, pl. <B>-mies.</B><DL COMPACT><DD> division into four parts, classes, branches, or other divisions. </DL>
<A NAME="tetracid">
<B>tetracid, </B>adjective, noun.<DL COMPACT><DD> (Chemistry.) <DD><I>adj. </I> <B>1. </B>(of a base or alcohol) having four hydroxyl (-OH) groups that may react with the hydrogen of an acid to form water, leaving a salt or ester. <DD><B> 2. </B>having four acid atoms of hydrogen per molecule. <DD><I>noun </I> a base or an alcohol having four replaceable hydroxyl (-OH) groups. </DL>
<A NAME="tetracyclic">
<B>tetracyclic, </B>adjective.<DL COMPACT><DD><B> 1. </B>passing through or having four cycles. <DD><B> 2. </B>(Chemistry.) having four rings in the molecule. <DD><B> 3. </B>(Botany.) having four whorls of floral organs. </DL>
<A NAME="tetracycline">
<B>tetracycline, </B>noun.<DL COMPACT><DD> an antibiotic used in treating a wide variety of bacterial diseases, including pneumonia, tuberculosis, meningitis, and dysentery. </DL>
<A NAME="tetrad">
<B>tetrad, </B>noun.<DL COMPACT><DD><B> 1. </B>a sum, group, or set of four. <DD><B> 2. </B>(Chemistry.) an element, atom, or radical with a valence of four. <DD><B> 3. </B>(Biology.) a group of four chromatids formed in various organisms when a pair of chromosomes splits longitudinally during meiosis. <DD><B> 4. </B>(Botany.) a group of four cells, as of spores or pollen grains. </DL>
<A NAME="tetradactyl">
<B>tetradactyl, </B>adjective.<DL COMPACT><DD> having four fingers, claws, toes, etc., on each limb. </DL>
<A NAME="tetradic">
<B>tetradic, </B>adjective.<DL COMPACT><DD> of or having to do with a tetrad. </DL>
<A NAME="tetradrachm">
<B>tetradrachm, </B>noun.<DL COMPACT><DD> a silver coin of ancient Greece, of the value of four drachmas. </DL>
<A NAME="tetradymite">
<B>tetradymite, </B>noun.<DL COMPACT><DD> (Mineralogy.) a telluride of bismuth, found in pale, steel-gray laminae with a bright, metallic luster. </DL>
<A NAME="tetradynamous">
<B>tetradynamous, </B>adjective.<DL COMPACT><DD> (Botany.) having six stamens, four longer, arranged in opposite pairs, and two shorter, inserted lower down (characteristic of flowers of the mustard family). </DL>
<A NAME="tetraethylammoniumchloride">
<B>tetraethylammonium chloride,</B><DL COMPACT><DD> a crystalline salt used as a drug to block the sympathetic nervous system during surgery, lower blood pressure in treating hypertensive conditions, etc. </DL>
<A NAME="tetraethyllead">
<B>tetraethyl lead,</B><DL COMPACT><DD> a poisonous, colorless liquid, used in gasoline to reduce knocking. (Abbr:) TEL (no periods). </DL>
<A NAME="tetraethylpyrophosphate">
<B>tetraethyl pyrophosphate,</B><DL COMPACT><DD> a crystalline compound, or a solution of it, used as an insecticide against mites and aphids, and in medicine as a stimulant in the treatment of certain diseases of the ocular, bulbar, and sacral nerves. (Abbr:) TEPP (no periods). </DL>
<A NAME="tetrafluoride">
<B>tetrafluoride, </B>noun.<DL COMPACT><DD> a fluoride with four atoms of fluorine. </DL>
<A NAME="tetrafluoroethylene">
<B>tetrafluoroethylene, </B>noun.<DL COMPACT><DD> a colorless, nonflammable gas used in making heat-resistant and acid-resistant plastics, such as Teflon. </DL>
<A NAME="tetragon">
<B>tetragon, </B>noun.<DL COMPACT><DD> a figure, especially a plane figure, having four angles and four sides, as a square or diamond. </DL>
<A NAME="tetragonal">
<B>tetragonal, </B>adjective.<DL COMPACT><DD><B> 1. </B>of or having to do with a tetragon; having four angles. <DD><B> 2. </B>designating or having to do with a system of crystallization (<B>tetragonal system</B>) in which the three axes are at right angles, the two lateral axes being equal and the vertical of a different length; dimetric. adv. <B>tetragonally.</B> </DL>
<A NAME="tetragram">
<B>tetragram, </B>noun.<DL COMPACT><DD><B> 1. </B>a word of four letters, especially the Tetragrammaton. <DD><B> 2. </B>(Geometry.) a figure formed by four straight lines in a plane and their six points of intersection; quadrilateral. </DL>
<A NAME="tetragrammaton">
<B>Tetragrammaton, </B>noun.<DL COMPACT><DD> the mysterious and sacred Hebrew word of four consonants, transliterated YHWH, YHVH, JHWH, or JHVH, standing for the Ineffable Name of God. The name is usually transcribed in English as <I>Yahweh</I> or <I>Jehovah.</I> </DL>
<A NAME="tetragrammaton">
<B>tetragrammaton, </B>noun.<DL COMPACT><DD> a word of four letters used as a symbol. </DL>
<A NAME="tetrahedral">
<B>tetrahedral, </B>adjective.<DL COMPACT><DD><B> 1. </B>of or having to do with a tetrahedron; having four faces. <DD><B> 2. </B>(Crystallography.) belonging to a division of the isometric system of which the regular tetrahedron is the characteristic form. adv. <B>tetrahedrally.</B> </DL>
<A NAME="tetrahedrite">
<B>tetrahedrite, </B>noun.<DL COMPACT><DD> (Mineralogy.) native sulfide of antimony and copper, with various elements sometimes replacing one or the other of these, often occurring in tetrahedral crystals. </DL>
<A NAME="tetrahedron">
<B>tetrahedron, </B>noun, pl. <B>-drons,</B> <B>-dra.</B><DL COMPACT><DD> (Geometry.) a solid figure having four faces. The most common tetrahedron is a pyramid whose base and three sides are equilateral triangles. </DL>
<A NAME="tetrahydrocannabinol">
<B>tetrahydrocannabinol, </B>noun.<DL COMPACT><DD> the active principle in marijuana and hashish, obtained from the resin of the hemp plant or produced synthetically. (Abbr:) THC (no periods). </DL>
<A NAME="tetrahydrofuran">
<B>tetrahydrofuran, </B>noun.<DL COMPACT><DD> a flammable liquid ether, used as a chemical intermediate and as a solvent for vinyl resins. (Abbr:) THF (no periods). </DL>
<A NAME="tetrahydroxy">
<B>tetrahydroxy, </B>adjective.<DL COMPACT><DD> (Chemistry.) having four hydroxyl (-OH) radicals. </DL>
<A NAME="tetralogy">
<B>tetralogy, </B>noun, pl. <B>-gies.</B><DL COMPACT><DD><B> 1. </B>a series of four connected dramas, operas, or other dramatic or literary works. <DD><B> 2. </B>(in ancient Greece) a series of four dramas, three tragic (the trilogy) and one satiric, exhibited at Athens at the festival of Dionysus. <DD><B> 3. </B>any set of four things. <BR> <I>Ex. a tetralogy of speeches, a tetralogy of congenital defects.</I> </DL>
<A NAME="tetralogyoffallot">
<B>tetralogy of Fallot,</B> <B>=Fallot's tetralogy.</B></DL>
<A NAME="tetramer">
<B>tetramer, </B>noun.<DL COMPACT><DD> a chemical compound in which four molecules of the same substance are produced by polymerization. </DL>
<B>tetramerous, </B>adjective.<DL COMPACT><DD><B> 1. </B>having, consisting of, or characterized by four parts. <DD><B> 2. </B>(Botany.) (of a flower) having four members in each whorl (generally written <I>4-merous</I>). <DD><B> 3. </B>(Zoology.) having tarsi with four joints. </DL>
