opponens pollicis
/əˌpəʊnənz ˈpɒlɪsɪs/Anatomy and Zoology
noun
A muscle of the hand, originating from the trapezium and flexor retinaculum and inserting into the first metacarpal, which serves to cup the palm and assist in the opposing of the thumb to the other fingers.
Origin
Mid 18th century. From scientific Latin opponens pollicis from classical Latin oppōnēns, + pollicis, genitive singular of pollex thumb.