ash crack is 'crack' or a joke that is in no way, shape or form the slightest bit funny and makes a man want to cry. Something that is said to be ash crack can be a poor effort of sarcasm or a comment that is intended to be funny but everything falls still and stops breathing, dies a little and commonly tumble weeds roll across scenery. People have been known to have that bad 'ash crack' that they have been put inside tyres and burnt alive (worse case scenario) common punishments include slaps and verbal abuse. 'Ash' can also mean 'dead'
A: 'pass me them turkey twizlers'
B: ' I turkey twizzled your mum'
A: ' NO, that was ash crack'
B: ' yer right in her crack'
(que tumble weed, verbal abuse and wet fish slap)
e.g. somebody starts telling a really long crap joke. You yell 'Just bore off with your ash crack, your giving me a boregasm!'