Whilst receiving deep-throat fellatio from a woman, one may stuff one's ballsack into the woman's mouth at the same time, the sheer volume of which causes her lips and cheeks to stretch wide open (as though she's making a big happy smile, hence it is sometimes referred to as a happy meal.)
A word to describe the sluttiest of all sluts. The exponential, factorial and absolute value of slut. The square root of "too slutty" if such a thing even existed.