1.AdverbWith great effort, vigour or gusto, or to the point of excess.
"I've been working my arse off all day for a measly few quid.; What a gig! The band played their arses off.; We partied our arses off all night long.; I didn't notice – I was too busy laughing my arse off!"
2.AdverbUsed as a general negative intensifier: to an extreme degree.
"I remember how we were all sweating our arses off during that heatwave.; I could be sitting on a beach somewhere rather than freezing my arse off in this dump."
3.AdverbSo as to rigorously exercise or exhaust someone.
"The boss has been working our arses off all week.; He may be 50 years old, but he could still run your arse off."