Ass play, or assplay, is a term generally used to refer to spreading and insertion of the anus by sex toys, fists and fingers. Ass play can be done as foreplay, to help someone loosen up before anal intercourse or simply to give the recipient pleasure. Ass play is generally a term used by gay men.
Ass play can involve a variety of different kinds of insertion but does not involve anal intercourse. It can include anal insertion of a finger or fingers, fisting, insertions by dildos, butt plugs, speculums, etc. Ass play can be done to a partner or can be done to alone as masturbation or a part of masturbation.