a muscle shirt or wife beater that is unnecessarily long, usually at least halfway down the thighs, that looks like it's a skirt if you don't know what it is
Pascal: Check out this wife beater, it really accentuates my pecs, don't you think?
Sam: Sure, but why did you get such a long one?
Pascal: It's not that long, I just wanted to get-
Sam: A muscle skirt?
Pascal: It's not a muscle skirt.
Sam: Yes it is! Go look in a mirror, it's almost down to your knees!