Wordnet 3.0
NOUN (1)
1.
eyeglasses having two focal lengths, one for near vision and the other for far vision;
The Collaborative International Dictionary of English v.0.48:
Bifocals \Bi"fo`cals\, n. pl. [Pref. bi-+ focal.]
eyeglasses whose lenses have two foci, allowing the wearer to
see both far and nearby objects clearly. The lenses are
partitioned horizontally, the upper and lower parts having
different focal lengths.
[PJC]
WordNet (r) 3.0 (2006):
bifocals
n 1: eyeglasses having two focal lengths, one for near vision
and the other for far vision
Moby Thesaurus II by Grady Ward, 1.0:
30 Moby Thesaurus words for "bifocals":
Polaroid glasses, blinkers, cheaters, colored glasses,
contact lens, dark glasses, divided spectacles, eyeglass,
eyeglasses, glasses, goggles, granny glasses, harlequin glasses,
horn-rimmed glasses, lorgnette, lorgnon, mini-specs, monocle,
nippers, pair of glasses, peepers, quizzing glass, readers,
reading glasses, shades, specs, spectacles, sun-specs, sunglasses,
trifocals