biceps
Pronunciation: /ˈbʌɪsɛps/
noun ( plural )
- any of several muscles having two points of attachment at one end, in particular:
- (also biceps brachii /ˈbreɪkɪʌɪ/) a large muscle in the upper arm which turns the hand to face palm uppermost and flexes the arm and forearm: he clenched his fist and exhibited his bulging biceps
- (also biceps femoris /fɪˈmɔːrɪs/ or leg biceps) Anatomy a muscle in the back of the thigh which helps to flex the leg.

Origin:
mid 17th century: from Latin, literally 'two-headed', from bi- 'two' + -ceps (from caput 'head')

Spelling help
The plural of biceps is the same as the singular: biceps.