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general::
Phrase(s): get off one’s ass [and] get off one’s rear; get off one’s butt
Sl. to get up and get busy; to stop loafing and get to work. (Caution with ass. Butt is also offensive to some people.) • Get off your ass and get busy! • It’s time you got off your butt and started to work.
McGrawhill's American Idioms And Phrasal Verbs