Crossword Dictionary

What's The Definition Of Optic?

\Op"tic\, n. [From {Optic}, a.] 1. The organ of sight; an eye. The difference is as great between The optics seeing, as the object seen. --Pope. 2. An eyeglass. [Obs.] --Herbert.
\Op"tic\, Optical \Op"tic*al\, a. [F. optique, Gr. ?; akin to ? sight, ? I have seen, ? I shall see, and to ? the two eyes, ? face, L. oculus eye. See {Ocular}, {Eye}, and cf. {Canopy}, {Ophthalmia}.] 1. Of or pertaining to vision or sight. The moon, whose orb Through optic glass the Tuscan artist views. --Milton. 2. Of or pertaining to the eye; ocular; as, the optic nerves (the first pair of cranial nerves) which are distributed to the retina. See Illust. of {Brain}, and {Eye}. 3. Relating to the science of optics; as, optical works. {Optic angle} (Opt.), the angle included between the optic axes of the two eyes when directed to the same point; -- sometimes called {binocular parallax}. {Optic axis}. (Opt.) (a) A line drawn through the center of the eye perpendicular to its anterior and posterior surfaces. In a normal eye it is in the direction of the optic axis that objects are most distinctly seen. (b) The line in a doubly refracting crystal, in the direction of which no double refraction occurs. A uniaxial crystal has one such line, a biaxial crystal has two. {Optical circle} (Opt.), a graduated circle used for the measurement of angles in optical experiments. {Optical square}, a surveyor's instrument with reflectors for laying off right angles.