<B>OPA</B> (no periods),<DL COMPACT><DD> Office of Price Administration. </DL>
<A NAME="opacification">
<B>opacification, </B>noun.<DL COMPACT><DD><B> 1. </B>the act of opacifying. <DD><B> 2. </B>the state of being opacified. </DL>
<A NAME="opacify">
<B>opacify, </B>transitive verb, intransitive verb, <B>-fied,</B> <B>-fying.</B><DL COMPACT><DD> to make or become opaque. </DL>
<A NAME="opacity">
<B>opacity, </B>noun, pl. <B>-ties.</B><DL COMPACT><DD><B> 1. </B>the quality or condition of being opaque; being impervious to light; darkness. <BR> <I>Ex. The small triangular area ... at the edge of the nebula is a dark cloud of very high opacity (Scientific American).</I> <DD><B> 2. </B>the quality or condition of being impervious, as to heat or sound. <DD><B> 3. </B>(Figurative.) obscurity of meaning. <DD><B> 4. </B>something opaque. <DD><B> 5. </B>(Figurative.) denseness or stupidity. </DL>
<A NAME="opah">
<B>opah, </B>noun.<DL COMPACT><DD> a large, brilliantly colored deepsea fish, found especially in the warmer parts of the Atlantic Ocean. </DL>
<A NAME="opal">
<B>opal, </B>noun, adjective.<DL COMPACT><DD><I>noun </I> a mineral, any of various forms of silica. Opals are somewhat like quartz. They are valued as gems and come in many varieties and colors. Certain opals reflect light with a peculiar rainbow play of color. Black opals show brilliant colored lights against a dark background; some are so dark as to seem almost black. Milk opals are milky white with rather pale lights. Fire opals are similar with more red and sometimes yellow flashes of color. <DD><I>adj. </I> like an opal. <BR> <I>Ex. The opal murmuring sea (Jean Ingelow).</I> </DL>
<A NAME="opalescence">
<B>opalescence, </B>noun.<DL COMPACT><DD> a play of colors like that of an opal. </DL>
<A NAME="opalescent">
<B>opalescent, </B>adjective.<DL COMPACT><DD> having a play of colors like that of an opal, especially the milk opal. </DL>
<A NAME="opalesque">
<B>opalesque, </B>adjective.<DL COMPACT><DD> like an opal; opalescent. </DL>
<A NAME="opaleye">
<B>opaleye, </B>noun, pl. <B>-eyes</B> or (collectively) <B>-eye.</B><DL COMPACT><DD> a greenish, herbivorous fish found off the California coast, sometimes used for food; greenfish. </DL>
<A NAME="opalglass">
<B>opal glass,</B><DL COMPACT><DD> a glass with a milky-white appearance caused by the addition of small colloidal particles which disperse the light passing through it; milk glass. </DL>
<A NAME="opaline">
<B>opaline, </B>adjective, noun.<DL COMPACT><DD><I>adj. </I> of or like opal; opalescent. <DD><I>noun </I> <B>=opal glass.</B> </DL>
<A NAME="opaque">
<B>opaque, </B>adjective, noun.<DL COMPACT><DD><I>adj. </I> <B>1a. </B>not letting light through; not transparent. <BR> <I>Ex. A brick wall is opaque. The water is so charged with mud and sand that it is opaque (Francis Parkman).</I> <DD><B> b. </B>not conducting energy or radiation, as heat, sound, or electricity. <BR> <I>Ex. Even on the clearest day, the atmosphere is as opaque to many kinds of radiation as if it were an ocean of ink (Time).</I> <DD><B> 2. </B>not shining; dark; dull. <BR> <I>Ex. an opaque star, an opaque light.</I> <DD><B> 3. </B>(Figurative.) hard to understand; obscure. <BR> <I>Ex. The Critique of Political Economy ... had baffled even Marx's disciples by its relentless and opaque abstraction (Edmund Wilson).</I> <DD><B> 4. </B>(Figurative.) stupid; dense. <DD><I>noun </I> <B>1. </B>something opaque. <DD><B> 2. </B>(Photography.) a pigment used to shade parts of a negative. adv. <B>opaquely.</B> noun <B>opaqueness.</B> </DL>
<A NAME="opaqueprojector">
<B>opaque projector,</B><DL COMPACT><DD> a projector having a mirror and lens to throw the image of a drawing, book's page, or other opaque object on a screen. </DL>
<A NAME="op">
<B>op</B> or <B>Op art,</B><DL COMPACT><DD> a form of abstract art in which unusual optical illusions and effects are produced by means of complex geometrical designs; optical art. <BR> <I>Ex. There is an obvious but superficial sense in which Op art ... can be called mathematical art. This aspect of Op is certainly not new. Hardedge, rhythmic, decorative patterns are as ancient as art itself, and even the modern movement toward abstraction in painting began with the geometric forms of the cubists (Scientific American).</I> </DL>
<A NAME="op">
<B>op</B> or <B>Op artist,</B><DL COMPACT><DD> a painter or sculptor who produces op art; optical artist. <BR> <I>Ex. The Op artists ... compose wavy lines of black and white, combinations and juxtaposition of color so abrupt that they deceive the optical sense (Alistair Cooke).</I> </DL>
<A NAME="opcit">
<B>op. cit.,</B><DL COMPACT><DD> in the work (previously) cited; in the book or article referred to (Latin, <I>opere citato</I>). </DL>
<A NAME="ope">
<B>ope, </B>verb, <B>oped,</B> <B>oping,</B> adjective.<DL COMPACT><DD> (Archaic.) <DD><I>v.t., v.i. </I> to open. <BR> <I>Ex. Lord, ope their eyes that they may see! (John Greenleaf Whittier).</I> <DD><I>adj. </I> open. <BR> <I>Ex. With both eyes wide ope (Robert Browning).</I> </DL>
<A NAME="opec">
<B>Opec</B> or <B>OPEC, </B>noun, or <B>O.P.E.C.</B><DL COMPACT><DD> Organization of Petroleum Exporting Countries. </DL>
<A NAME="opedpage">
<B>Op-Ed page,</B> or <B>Op-Ed, </B>noun.<DL COMPACT><DD> (U.S.) a newspaper page featuring articles by columnists and other writers. <BR> <I>Ex. ... the Op-Ed provides a variety of viewpoints in dozens of major metropolitan dailies (Time).</I> </DL>
