sit on (one's) arse

sit on (one's) arse

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