Someone, (usually a female), who just lays there, unmoving, as they are getting fucked.

A swimmer

A sexual partner (usually female) who is not actively involved in the sexual encounter.

what a butthole looks like.

When having sex with a really inexperienced female who lays on her back with her arms out above her head, legs apart and doesn't really do much other than that - like a star fish.

the small cross shape made by the sphincter muscle or the clenching of the arsehole, sometimes called the 'ringpiece' or the 'rusty sheriff's badge'

Sea Stars. A common name for a class of echinoderms called astoidea. They have five sides and live underwater, commonly feeding on smaller creatures like snails, sponges, bivalves and deposits of algae.