A mcmac is the sexual action of filling a womans vagina with big mac secret sauce then eating it out, therefore bypassing the unbearable fishy taste associated with a vagina.

the thing that you don’t have when you’re phones percentage is over 20

The most delicious and fattening of all McDonald's products. It can only be ordered from their secret menu, to access this secret menu you must punch a cashier in the face while shouting McMAC!! repeatedly. If the cashier is still alive, he must then (company rules) proceed to give you a McMac.