:1) To be having such a shitty day that you feel like you're wearing a Five Pound Mud Hat. 2) To be on the receiving end of a tubgirl. 3) To have your head so far up your ass that you're wearing a Five Pound Mud Hat.
And she was all, "you want me to give you a FivePound Mud Hat?" And I was like, "wtf's a FivePound Mud Hat?" And then she said, "why don't you look it up on urbandictionary.com ass hole."