The Collaborative International Dictionary of English v.0.48:
Amorpha \A*mor"pha\, n.; pl. Amorphas. [Gr. ? shapeless.] (Bot.) A genus of leguminous shrubs, having long clusters of purple flowers; false or bastard indigo. --Longfellow. [1913 Webster]WordNet (r) 3.0 (2006):
amorpha n 1: any plant of the genus Amorpha having odd-pinnate leaves and purplish spicate flowers