The Collaborative International Dictionary of English v.0.48:
bimolecular \bi"mo*lec"u*lar\, a. [Pref. bi- + molecular.] (Chem.) Pertaining to, involving, or formed from, two molecules; as, a bimolecular reaction (a reaction between two molecules). [Webster 1913 Suppl.]WordNet (r) 3.0 (2006):
bimolecular adj 1: relating to or affecting two molecules