sit on

Short definition from Wiktionary

Verb

1. 1
   To block, suppress, restrain (something).
2. 2
   To restrain (a person).
3. 3
   To take no action on (something); to hold (something) in reserve without actually using.
4. 4
   To be a member of (something).
5. 5
   To hold an official inquiry regarding (something); to deliberate about (something).
6. 6
   To insert (something) into one's vagina or anus from below.
7. 7
   Used other than figuratively or idiomatically: see sit, on.

Adjective

1. 1
   Designed to be sat on.