To attend a private meeting or class without participating.

(idiomatic) shove it up your ass (up yours) or back off. / Used other than figuratively or idiomatically: see sit on, sit, on, it.

(idiomatic) To block, suppress, restrain. / (idiomatic, informal) To restrain (a person). / (idiomatic) To take no action on; to hold in reserve without actually using. / To be a member of.

(idiomatic) To attend a class, educational presentation, meeting, etc. for one time, as a visitor. / (music) To take part in a group musical performance, especially a jazz session, as a temporary guest.

present participle of sit in

present participle of sit on it

A surname.

Designed to be sat on.

present participle of sit in for

To take care of children in the absence of their parents; to work as a babysitter for someone. / To serve as a model for an artist or as the subject of a piece of art.