The Collaborative International Dictionary of English v.0.48:

Bignoniaceous \Big*no`ni*a"ceous\, a. (Bot.)
   Of pertaining to, or resembling, the family of plants of
   which the trumpet flower (also called trumpet creeper and
   trumpet vine) is an example.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bignoniaceous
    adj 1: of or pertaining to or characteristic of plants of the
           family Bignoniaceae