triceps tri·ceps (trī'sěps')
n. pl. tri·ceps·es (-sěp'sĭz) or triceps
A three-headed muscle of the upper arm, whose long or scapular head has origin from the lateral border of the scapula, the lateral head, origin from the lateral and posterior surface of the humerus, and the medial head from the posterior surface of the humerus; with insertion into the olecranon of the ulna, with nerve supply from the radial nerve, and whose action extends the forearm; the triceps brachii.
The gastrocnemius and soleus muscles of the calf considered as one muscle; the triceps surae.