Source : Webster's Revised Unabridged Dictionary (1913)

Quadriceps \Quad"ri*ceps\, n. [NL., fr. L. qyattuor four + caput
   head.] (Anat.)
   The great extensor muscle of the knee, divided above into
   four parts which unite in a single tendon at the knee.

Source : WordNet®

quadriceps
     n : a muscle of the thigh that extends the leg [syn: {quadriceps
         femoris}, {musculus quadriceps femoris}, {quad}]