deltoid
Concise Oxford English Dictionary © 2008 Oxford University Press:
deltoid /ˈdɛltɔɪd/
▶adjective technical
- 1 triangular.
- 2 denoting a thick triangular muscle covering the shoulder joint and used for raising the arm away from the body.
– origin C18: from Fr. deltoïde, or via mod. L. from Gk deltoeidēs.
'deltoid' also found in these Oxford entries:

