rat's rear end
a way of saying that you don't care. used around people u shouldn't be calling the name of the rear end. ranges from kids to a corporate meeting.
Wife: Honey, Bush is on TV
Husband: who gives a rat's rear end
3 year old: daddy, u mean ass?
husband: O.o?
Husband: who gives a rat's rear end
3 year old: daddy, u mean ass?
husband: O.o?