Cleavecheese occurs when a woman is eating, and food particles accidentally spill into her cleavage.
The particles then ferment in this warm, cavernous environment and if left untreated, transform into a mold-like substance called cleavecheese.
"Dude, did you see Mrs. MacDonald's cleavecheese when she bent down? It was all brown and shit."
CB4 is a pseudonym for "cockblock". Friends do not CB4 friends, unless the woman is over 300 pounds or is a man. The term can be used in public settings.
"I had this chick down to her underwear, when Mort walked in a CB4'd me."