Entry 1 sense Webster, 1913 Bilinear · Bi·lin·e·ar · IPA /baɪˈlɪn.i.ɚ/ 01 a. Of, pertaining to, or included by, two lines; as, bilinear coördinates. 1. Of, pertaining to, or included by, two lines; as, bilinear coördinates.(Math.)