The growth of fuzz, hair, or fur on the lower back entering to the domain of one's buttocks; usually pertaining to the male race, but also including rather masculine females
American Man: Why, what is that lawn of hair on your lower back that?
European Woman: I think they're calling it assgrass.
When your using a public loo for a poo and someone goes into the cubicle next to you and does a really nastyloud smelly shit that is so offensive it makes you feel really unwell
I was in the shitters at the metro nipping one off when this guy went in the next cubicle and really dropped his guts, it was loud, splaterry and it stunk, I think it was an assgassination attempt!