Definition: A name given to several muscles of the fingers or toes, by the action of which these digits are opposed to the others. The opponens muscles of the hands act at the carpometacarpal joints, cupping the palm; this enables flexion at the metacarpophalangeal joints to oppose the thumb to the small finger or vice versa. Although comparable muscles in the foot are also called opponens, no true opposition occurs in the foot.
[L. op-pono (obp-), pres. p. -ens, to place against, oppose]