1
general::
Also, sit upon. 1. Confer about or deliberate over, as in Another attorney was called to sit on the case. [Mid-1400s] 2. Suppress or repress, as in I know they were sitting on some evidence. [Early 1900s] 3. Postpone action or resolution regarding, as in I don't know why the city council is sitting on their decision. [Early 1900s] 4. Rebuke sharply, rep rimand, as in If he interrupts one more time I'm going to sit on him. [Slang; second half of 1800s]
American Heritage Idioms
2
general::
Phrase(s): sit on someone or something
1. Lit. to place oneself in a sitting position on someone or something. • The enormous woman knocked the crook out and sat on him until the police came. • I need to sit on this chair for a minute and catch my breath. 2. Fig. to hold someone or something back; to delay someone or something. • The project cannot be finished because the city council is sitting on the final approval. • Ann deserves to be promoted, but the manager is sitting on her because of a disagreement. • It’s hard to do your best when you know that someone is sitting on you, and no matter what you do, it won’t help your advancement.
McGrawhill's American Idioms And Phrasal Verbs