An insultive phrase, denoting that you fuck somebody's mouth, that's not ever meant to be true, but it's always funny to tell it to your friends/enemies/dog/slaves/mailmen/mailwomen/pOsama Bin Laden]/anybody.
Osama Bin Laden: I am going to bomb 'mericans again.
'bama: If i had an eye on my dick, i'd see inside your mouth.
A slang term for the slang term smecks (sex), that just sounds better and can be used in many situations.
Derivatives: buttshmecks, queershmecks, boobshmecks/boobyshmecks, mouthshmecks, handshmecks and anything like that.