/em/ , n. , pl. M's or Ms, m's or ms .
1. the thirteenth letter of the English alphabet, a consonant.
2. any spoken sound represented by the letter M or m, as in my, summer, or him.
3. something having the shape of an M.
4. a written or printed representation of the letter M or m.
5. a device, as a printer's type, for reproducing the letter M or m.
6. Print. em.