The Collaborative International Dictionary of English v.0.48:

Biceps \Bi"ceps\, n. [L., two-headed; bis twice + caput head.
   See Capital.] (Anat.)
   A muscle having two heads or origins; -- applied particularly
   to a flexor in the arm, and to another in the thigh.
   [1913 Webster]

WordNet (r) 3.0 (2006):

biceps
    n 1: any skeletal muscle having two origins (but especially the
         muscle that flexes the forearm)