Understand that 'arse about' is casual British slang not to be used in formal situations.

British Slang

'Arse about' is mildly vulgar; some may find it offensive. Be cautious with your audience.

Mildly Vulgar

It's a metaphorical expression meaning to be unproductive, and does not involve a literal 'arse'.

Conveys a sense of playfulness or light-heartedness, appropriate among close friends.

Typically implies activities that are seen as fun or enjoyable but not serious.

Captures a nuance that is friendlier and less aimless than 'wasting time'.