Extensor

Ex-ten′sor

,

Noun.

[L., one who stretches. See

.]

(Anat.)

A muscle which serves to extend or straighten any part of the body, as an arm or a finger; – opposed to

flexor

.

,

Noun.

In anatomy, a muscle which serves to extend or straighten any part of the body, as an arm or a finger; opposed to flexor.

extensor ‎(plural extensors)

(anatomy) A muscle whose contraction extends or straightens a limb or body part.
- 2004, Jean-Pierre Hourdebaigt, Canine Massage: A Complete Reference Manual
  Starting at the point of shoulder, use muscle squeezings, picking-ups, kneadings and gentle frictions, interspersed with effleurages, over the triceps muscle as well as the fleshy part of the flexor and extensor muscle groups.

extensor m, f ‎(plural extensores)

extensor m ‎(plural extensores)