- (idiomatic) To block, suppress, restrain.
- The chairman sat on the report until the end of the legislative session.
- (idiomatic, informal) To restrain (a person).
- He started to act up, but she sat on him.
- (idiomatic) To take no action on
- I sent the boss my proposal three weeks ago and he's been just sitting on it.
- To be a member of
- He sits on the appropriations committee.