Quiz: Remember the definition of mal de mer?
1738, "involving both eyes," earlier "having two eyes" (1713), from French binoculaire, from Latin bini "two by two, twofold, two apiece" (see binary) + ocularis "of the eye," from oculus "eye" (see eye (n.)). The double-tubed telescopic instrument (1871, short for binocular glass) earlier was called a binocle. Related: Binocularity.
binocular bin·oc·u·lar (bə-nŏk'yə-lər, bī-)
Adapted to the use of both eyes. Used of an optical instrument.