m, the thirteenth letter of the english alphabet, is a vocal consonant, and from the manner of its formation, is called the labio-nasal consonant. see guide to pronunciation, // 178-180, 242.-as a numeral, m stands for one thousand, both in english and latin.-a quadrat, the face or top of which is a perfect square; also, the size of such a square in any given size of type, used as the unit of measurement for that type: 500 m's of pica would be a piece of matter whose length and breadth in pica m's multiplied together produce that number.-a brand or stigma, having the shape of an m, formerly impressed on one convicted of manslaughter and admitted to the benefit of clergy.