American Heritage Dictionary
(4)
Century Dictionary
(1)
GNU Webster's 1913
(2)
WordNet
(1)
Elsewhere on the web
The best way to check is to look at them and see if the bifocal is on the bottom.— Payson Roundup stories
I couldn't read out of the bifocal part, and since I was in Grad School and needed to read, the glasses were nearly useless.
Eyeglasses with bifocal or progressive lenses are the most common correction for presbyopia, adds Kevin Niksarli, MD of Manhattan Lasik Center.— PRWeb
I've got one, cuz some of those pills are too small for my bifocal eyes.— Hey, you!
Do you wear toric, bifocal, or another type of specialty lens?— LearnHub Activities

Bubble size: how much this word was used in a year
Bubble height: used more or less than expected, vs. all uses evenly distributed
You can expect to see this word about once a year.