Word Study
flexor
CIDE DICTIONARY
flexor, n. [NL.].
A muscle which bends or flexes any part; as, the flexors of the arm or the hand; -- opposed to extensor . [1913 Webster]
OXFORD DICTIONARY
flexor, n. (in full flexor muscle) a muscle that bends part of the body (cf. EXTENSOR).
Etymology
mod.L (as FLEX(1))
For further exploring for "flexor" in Webster Dictionary Online