to deliberately not do something/ to avoid something/ the act of ditching a person or thing.
variations: sack it/him/her off, sacking off.
A: wats good? wanna come cotch at mine?
B: cant, got an essay to do and some reading aswell, long.
A: sack it off - we'll smoke a joint and play pro instead.
A: Alex knew we were leaving at 7 where the fuck is he?
B: Allow it, sack him off we're going.
I've been a wasteman, sacking off all day.
A: you do your homework?
B: allow it, i sacked it off.