n. An abbreviation (in French) of Messieurs (gentlemen, sirs).n. An abbreviation of millimeter.An abbreviationof their Majesties;of Martyrs.An abbreviationof the plural of Latin words commonly abbreviated masculine, as magistri;of the Latin matrimonium;of the Latin meritissimus.An abbreviation of square millimeter.An abbreviation of cubic millimeter. μμ. A symbol used to denote a thousandth of a micron or a millionth of a millimeter.An abbreviation of Master of Mechanical Engineering.An abbreviation of magnetomotive force.