sit on (one's) arse

sit on (one's) arse

rude slang To be idle, especially when action is needed. Primarily heard in UK. You can't just sit on your arse all summer. Get a job, join a club—do something with your time! I was tired of sitting on my arse while so many people in the city needed help, so I decided to join a homeless shelter and try to lend a hand where I could.
See also: arse, on, sit