Does not mean an unfirm bottom, but it means a person who is very lazy
I had to fire David as he was a slack arse
de Windy28 3 septembre 2009
A word used for someone who receives anal a lot.
That girl Wendy over there, I heard the whole football team has put it up her arse. She must be a right slack arse.
de Yeahyea 8 juin 2015