triceps
Concise Oxford English Dictionary © 2008 Oxford University Press:
triceps /ˈtrʌɪsɛps/
▶noun (pl. same) Anatomy any of several muscles having three points of attachment at one end, particularly (also triceps brachii /ˈbreɪkɪʌɪ/) the large muscle at the back of the upper arm.
– origin C16: from L., lit. ‘three-headed’, from tri- ‘three’ + -ceps (from caput ‘head’).
'triceps' also found in these Oxford entries:

