tri•fo•calPronunciation: (trī-fō'kul, trī'fō"-), [key]
having three foci.
(of an eyeglass lens) having three portions, one for near, one for intermediate, and one for far vision.
eyeglasses with trifocal lenses.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.