1. em - Noun
2. em - Adjective
3. em - Pronoun
4. em - Interjection
5. Em - Proper noun
The portion of a line formerly occupied by the letter m, then a square type, used as a unit by which to measure the amount of printed matter on a page; the square of the body of a type.
Source: Webster's dictionarysince `em quad' is hard to distinguish from `en quad', printers sometimes called it a `mutton quad' Source: Internet