<B>pyrazine, </B>noun.<DL COMPACT><DD> (Chemistry.) <DD><B> 1. </B>a feebly basic, crystalline organic compound, with an odor like heliotrope. <DD><B> 2. </B>any one of various compounds derived from it. <BR> <I>Ex. The new TB medicine is a pyrazine chemical (Science News Letter).</I> </DL>
<A NAME="pyre">
<B>pyre, </B>noun.<DL COMPACT><DD><B> 1. </B>a pile of wood for burning a dead body as a funeral rite. <BR> <I>Ex. Only within the past century have grieving widows been restrained from throwing themselves on their husbands' funeral pyres (Newsweek).</I> <DD><B> 2. </B>any large pile or heap of burnable material. </DL>
<A NAME="pyrene">
<B>pyrene</B> (1), noun.<DL COMPACT><DD><B> 1. </B>a stone of a fruit, especially when there are several in one fruit. <DD><B> 2. </B><B>=nutlet.</B> </DL>
<A NAME="pyrene">
<B>pyrene</B> (2), noun.<DL COMPACT><DD> a solid hydrocarbon, obtained from coal tar. </DL>
<A NAME="pyrenean">
<B>Pyrenean, </B>adjective, noun.<DL COMPACT><DD><I>adj. </I> of or having to do with the Pyrenees, a mountain range between France and Spain. <BR> <I>Ex. Swarms of butterflies, dragonflies and other insects fly southwards over the Pyrenean passes (Observer).</I> <DD><I>noun </I> <B>1. </B>a native or inhabitant of the Pyrenees. <DD><B> 2. </B><B>=Great Pyrenees.</B> </DL>
<B>pyrenoid, </B>noun.<DL COMPACT><DD> a small protein structure resembling a nucleus, found in the chloroplast of certain algae, and associated with the formation and accumulation of starch. </DL>
<A NAME="pyrethrin">
<B>pyrethrin, </B>noun.<DL COMPACT><DD> one of the constituents or active principles of pyrethrum. <BR> <I>Ex. Insects cannot build resistance to pyrethrins because they are a natural insecticide (Cape Times).</I> </DL>
<A NAME="pyrethrum">
<B>pyrethrum, </B>noun, pl. <B>-thrums.</B><DL COMPACT><DD><B> 1. </B>any one of various chrysanthemums, much cultivated for their showy while, lilac, or red flowers. <BR> <I>Ex. The rich "white highlands" whence comes most of Kenya's lucrative coffee, tea, sisal and pyrethrum (Time).</I> <DD><B> 2. </B>an insecticide made of the powdered flower heads of any of certain of these. <BR> <I>Ex. With the appearance of the scientists on the field of battle, the old stand-bys of pyrethrum, oils and arsenic compounds were developed (Science News Letter).</I> </DL>
<A NAME="pyretic">
<B>pyretic, </B>adjective.<DL COMPACT><DD><B> 1. </B>of or having to do with fever. <DD><B> 2. </B>producing fever. <BR> <I>Ex. Whenever the bodily temperature falls below normal, pyretic treatment is demanded (H. C. Wood).</I> <DD><B> 3. </B><B>=feverish.</B> </DL>
<A NAME="pyretology">
<B>pyretology, </B>noun.<DL COMPACT><DD> the science of, or accumulated knowledge of, fevers. </DL>
<A NAME="pyretotherapy">
<B>pyretotherapy, </B>noun.<DL COMPACT><DD> therapy in which fever is induced in the patient. </DL>
<A NAME="pyrex">
<B>Pyrex, </B>noun.<DL COMPACT><DD> (Trademark.) a kind of glassware that will not break when heated. <BR> <I>Ex. One of the newest glasses is borosilicate glass, widely advertised under the trade name "Pyrex" (Monroe M. Offner).</I> </DL>
<A NAME="pyrexia">
<B>pyrexia, </B>noun. <B>=fever.</B></DL>
<A NAME="pyrexial">
<B>pyrexial, </B>adjective.<DL COMPACT><DD> of or having to do with a fever. </DL>
<A NAME="pyrexic">
<B>pyrexic, </B>adjective. <B>=feverish.</B></DL>
<A NAME="pyrgeometer">
<B>pyrgeometer, </B>noun.<DL COMPACT><DD> an instrument for measuring the heat radiated outward into space from the earth's surface. </DL>
<A NAME="pyrheliometer">
<B>pyrheliometer, </B>noun.<DL COMPACT><DD> an instrument for measuring the intensity of the sun's heat. </DL>
<A NAME="pyribenzamine">
<B>Pyribenzamine, </B>noun.<DL COMPACT><DD> (Trademark.) an antihistamine used especially in treating allergies. </DL>
<A NAME="pyridic">
<B>pyridic, </B>adjective.<DL COMPACT><DD> of or related to pyridine. </DL>
<A NAME="pyridin">
<B>pyridin, </B>noun. <B>=pyridine.</B></DL>
<A NAME="pyridine">
<B>pyridine, </B>noun.<DL COMPACT><DD> a liquid organic base with a pungent odor, occurring especially in coal tar, and serving as the parent substance of many compounds. It is used as a solvent and waterproofing agent, and in making various drugs and vitamins. </DL>
<A NAME="pyridoxal">
<B>pyridoxal, </B>noun.<DL COMPACT><DD> an aldehyde or pyridoxine found in certain enzymes, such as carboxylase, and important in the synthesis of amino acids. </DL>
<A NAME="pyridoxin">
<B>pyridoxin, </B>noun. <B>=pyridoxine.</B></DL>
<A NAME="pyridoxine">
<B>pyridoxine, </B>noun.<DL COMPACT><DD> vitamin B-6, essential to human nutrition, found especially in wheat germ, yeast, fish, and liver; adermin. </DL>
<B>pyrimethamine, </B>noun.<DL COMPACT><DD> a synthetic drug used in the treatment of malaria, often in combination with primaquine or chloroquine, and experimentally against some other diseases. <BR> <I>Ex. The antimalarial drug pyrimethamine ... is also quite effective against toxoplasmosis (F. P. Mathews).</I> </DL>
<A NAME="pyrimidine">
<B>pyrimidine, </B>noun.<DL COMPACT><DD><B> 1. </B>a liquid or crystalline organic base with a strong odor, whose molecular arrangement is a six-membered ring containing atoms of nitrogen. It is found in living matter and is a constituent of nucleic acid. <DD><B> 2. </B>any one of a group of compounds derived from it, such as cytosine and thymine. </DL>
<A NAME="pyrite">
<B>pyrite, </B>noun, pl. <B>-rites.</B><DL COMPACT><DD> a common yellow mineral with a metallic luster, a compound of iron and sulfur, which looks like and is often mistaken for gold; iron pyrites; fool's gold. It is used in making sulfuric acid. <BR> <I>Ex. Pyrite, in mistake for gold, was the first mineral shipped from America to England (W. R. Jones).</I> </DL>
<A NAME="pyrites">
<B>pyrites, </B>noun.<DL COMPACT><DD><B> 1. </B>any one of various compounds of sulfur and a metal, such as tin pyrites, an ore of tin, or copper pyrites. <DD><B> 2. </B><B>=pyrite.</B> </DL>
<A NAME="pyritic">
<B>pyritic, </B>adjective.<DL COMPACT><DD><B> 1. </B>having to do with pyrites. <DD><B> 2. </B>consisting of or resembling pyrites. </DL>
<B>pyro-,</B><DL COMPACT><DD> (combining form.) <DD><B> 1. </B>of, having to do with, using, or caused by fire. <BR> <I>Ex. Pyromania = an obsession with fire. Pyrotechnics = the making of fireworks.</I> <DD><B> 2. </B>heat; high temperatures. <BR> <I>Ex. Pyrometer = an instrument that measures high temperatures.</I> <DD><B> 3. </B>formed by heat. <BR> <I>Ex. Pyroacid = an acid formed by heat.</I> <DD> Also, <B>pyr-</B> before <I>h</I> and some vowels. </DL>
<A NAME="pyroacid">
<B>pyroacid, </B>noun.<DL COMPACT><DD> any one of various acids obtained by subjecting other acids to heat. </DL>
<B>pyrocatechol, </B>noun.<DL COMPACT><DD> a colorless, crystalline benzene derivative, occurring especially in certain plants and prepared from phenol by distillation of catechin. It is used in photography as a developer and medicinally as an antiseptic. </DL>
<A NAME="pyroceram">
<B>Pyroceram, </B>noun.<DL COMPACT><DD> (Trademark.) a light, crystalline ceramic material or product made from glass-ceramic and able to withstand sudden and extreme temperature and heat changes. <BR> <I>Ex. Pyroceram can be used to make items ranging from cooking pans to airplane skins (Wall Street Journal).</I> </DL>
<A NAME="pyrochemical">
<B>pyrochemical, </B>adjective.<DL COMPACT><DD> having to do with or producing chemical changes at high temperatures. adv. <B>pyrochemically.</B> </DL>
<A NAME="pyroclastic">
<B>pyroclastic, </B>adjective.<DL COMPACT><DD> composed chiefly of fragments of volcanic origin. <BR> <I>Ex. pyroclastic flows, pyroclastic texture. Agglomerate and tuff are pyroclastic rocks.</I> </DL>
<A NAME="pyroconductivity">
<B>pyroconductivity, </B>noun.<DL COMPACT><DD> electrical conductivity induced by heat. </DL>
<A NAME="pyrocrystalline">
<B>pyrocrystalline, </B>adjective.<DL COMPACT><DD> crystallized from a molten magma or highly heated solution. </DL>
<A NAME="pyroelectric">
<B>pyroelectric, </B>adjective, noun.<DL COMPACT><DD><I>adj. </I> of, having to do with, or having pyroelectricity. <DD><I>noun </I> a pyroelectric crystal. </DL>
<A NAME="pyroelectricity">
<B>pyroelectricity, </B>noun.<DL COMPACT><DD><B> 1. </B>the electrified state or electric polarity produced in certain crystals by a change in temperature. <DD><B> 2. </B>the part of physics dealing with such phenomena. </DL>
<A NAME="pyrogallate">
<B>pyrogallate, </B>noun.<DL COMPACT><DD> an ether of pyrogallol. </DL>
<A NAME="pyrogallic">
<B>pyrogallic, </B>adjective.<DL COMPACT><DD> obtained from gallic acid by the action of heat. </DL>
<A NAME="pyrogallicacid">
<B>pyrogallic acid,</B> <B>=pyrogallol.</B></DL>
<A NAME="pyrogallol">
<B>pyrogallol, </B>noun.<DL COMPACT><DD> a white, crystalline compound obtained by heating gallic acid with water, used as a photographic developer, in medicine, and as a reagent. Pyrogallol is a phenol but can be regarded as an acid. </DL>
<A NAME="pyrogen">
<B>pyrogen, </B>noun.<DL COMPACT><DD> a substance that, when introduced into the blood, produces fever. <BR> <I>Ex. Pyrogens in pure form can, with advantage, replace the older materials and methods for producing a general stimulation of the defense mechanisms of the body (London Times).</I> </DL>
<A NAME="pyrogenic">
<B>pyrogenic, </B>adjective.<DL COMPACT><DD><B> 1. </B>producing heat or fever. <DD><B> 2. </B>produced by fire. <BR> <I>Ex. Volcanic rock is pyrogenic.</I> </DL>
