A muscle in the manus that functions to adduct the thumb. It has two heads: transverse and oblique. It is a fleshy, flat, triangular, and fan-shaped muscle deep in the thenar compartment beneath the long flexor tendons and the lumbrical muscles at the center of the palm. It overlies the metacarpal bones and the interosseous muscles[WP]. [ http://en.wikipedia.org/wiki/Adductor_pollicis_muscle ]