A mouthole is a conjunction of the words "mouth" and "hole". The term refers to the oral area between the lips, where various objects are shoved down for a number of purposes. The term is often used sexually, but occasionally is used for other purposes in the same context. The term "mouthole", as well as the official spelling was coined c. September 2010 by Michael Bornemann, who is quite famous for his use of "hole" in words under the premise that any word with the suffix "hole" in the back makes the root word up to 60% dirtier and therefore substantially more comical.
Jacob: Oh me oh my, fucking harlots these days...
Michael: I hear you bro, they always got something down their mouthole
Michael: God damn, I'm so hungry-_-...I should've had breakfast
Brandon: Here, take this Poptart!
Michael: Aww sweet, I'm gonna enjoy this in my mouthole. :3