The Collaborative International Dictionary of English v.0.48:

Bean trefoil \Bean" tre"foil\ (Bot.)
   A leguminous shrub of southern Europe, with trifoliate leaves
   (Anagyris foetida).
   [1913 Webster]

WordNet (r) 3.0 (2006):

bean trefoil
    n 1: shrub with trifoliate leaves and yellow flowers followed by
         backward curving seed pods; leaves foetid when crushed
         [syn: bean trefoil, stinking bean trefoil, Anagyris
         foetida]