1. The letter m.
2. Printing.
   1. The width of a square or nearly square piece of type, used as a unit of measure for matter set in that size of type.
   2. Such a measure for 12-point type; a pica.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.