Source : Webster's Revised Unabridged Dictionary (1913)

Bimolecular \Bi"mo*lec"u*lar\, a. [Pref. bi- + molecular.]
   (Chem.)
   Pertaining to, or formed from, two molecules; as, a
   bimolecular reaction (a reaction between two molecules).

Source : WordNet®

bimolecular
     adj : relating to or affecting two molecules