trifocal
Concise Oxford English Dictionary © 2008 Oxford University Press:
trifocal/trʌɪˈfəʊk(ə)l/
▶adjective (of a pair of glasses) having lenses with three parts with different focal lengths. ▶noun (trifocals) a pair of trifocal glasses.
'trifocal' also found in these Oxford entries:

