"lying or situated in two planes," 1849; see bi- "two" + planar.
Entries linking to biplanar
bi-
word-forming element meaning "two, having two, twice, double, doubly, twofold, once every two," etc., from Latin bi- "twice, double," from Old Latin dvi- (cognate with Sanskrit dvi-, Greek di-, dis-, Old English twi-, German zwei- "twice, double"), from PIE root *dwo- "two."
Nativized from 16c. Occasionally bin- before vowels; this form originated in French, not Latin, and might be partly based on or influenced by Latin bini "twofold" (see binary). In chemical terms, it denotes two parts or equivalents of the substance referred to. Cognate with twi- and di- (1).
planar adj.
"lying in or otherwise related to a plane, flat," 1850, from Latin planaris "level, flat," from planum "plane" (from PIE root *pele- (2) "flat; to spread"). An earlier word in the same sense was planary (1660s).