A very soft (mushy) bowel movement in which an individual wipes their anus over and over again without any great success, resulting in an itchy butt, and the use of a whole roll of toilet paper.
Dude! Why is it that you always get mush tush at my house?! You owe me some Charmin you stinky bastard!
A person you hate intensely not because they deserve such hatred but because they serve as a focus for your general hatred. A healthy way to dispense with excess animosity.
Jake's not really that big an asshole. He just serves as my hate sink.