opa

n. [ L. opacitas: cf. F. opacité. ] 1. The state of being opaque; the quality of a body which renders it impervious to the rays of light; want of transparency; opaqueness. [ 1913 Webster ]

2. Obscurity; want of clearness. Bp. Hall. [ 1913 Webster ]

a. [ L. opacus. See Opaque. ] Opaque. [ R. ] Milton. -- O*pa"cous*ness, n. [R.] [1913 Webster]

a. Opaque. [ Obs. ] Sterne. [ 1913 Webster ]

n. (Zool.) A large oceanic fish (Lampris guttatus), inhabiting the Atlantic Ocean. It is remarkable for its brilliant colors, which are red, green, and blue, with tints of purple and gold, covered with round silvery spots. Called also king of the herrings. [ 1913 Webster ]

a. See Opaque. [ 1913 Webster ]

n. [ L. opalus: cf. Gr. &unr_;, Skr. upala a rock, stone, precious stone: cf. F. opale. ] (Min.) A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity. [ 1913 Webster ]

☞ The precious opal presents a peculiar play of colors of delicate tints, and is highly esteemed as a gem. One kind, with a varied play of color in a reddish ground, is called the harlequin opal. The fire opal has colors like the red and yellow of flame. Common opal has a milky appearance. Menilite is a brown impure variety, occurring in concretions at Menilmontant, near Paris. Other varieties are cacholong, girasol, hyalite, and geyserite. [ 1913 Webster ]

v. i. [ imp. & p. p. Opalesced p. pr. & vb. n. Opalescing ] To give forth a play of colors, like the opal. [ 1913 Webster ]

n. (Min.) A reflection of a milky or pearly light from the interior of a mineral, as in the moonstone; the state or quality of being opalescent. [ 1913 Webster ]