olecranon

from WordNet (r) 3.0 (2006)

olecranon
    n 1: process of the ulna that forms the outer bump of the elbow
         and fits into the fossa of the humerus when the arm is
         extended [syn: {olecranon}, {olecranon process}]

from The Collaborative International Dictionary of English v.0.48

Olecranon \O*lec"ra*non\, n. [NL., fr. Gr. ?; ? elbow + krani`on
   the head.] (Anat.)
   The large process at the proximal end of the ulna which
   projects behind the articulation with the humerus and forms
   the bony prominence of the elbow.
   [1913 Webster]