trifocal adjective & noun. [trʌɪ'fǝʊk(ǝ)l] E19.
[from TRI- + FOCAL.]
A. adjective.
1. Of spectacles: having three pairs of lenses in one frame. rare. Only in E19.

2. (Of a lens) having three parts with different focal lengths; (of spectacles) having such lenses. E20.
b. noun. A trifocal lens; (usu. in pl.) trifocal spectacles. L19.

[TahlilGaran] English Dictionary ▲