Mr.

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Mister. Used as a courtesy title before the surname or full name of a man.
• noun Used in informal titles for a man to indicate the epitomizing of an attribute or activity.

from The Century Dictionary.

• noun An abbreviation of Master or Mister.
• noun An abbreviation of millier.
• noun An abbreviation of Member of the Royal Institution.

from the GNU version of the Collaborative International Dictionary of English.

• The customary abbreviation of Mister in writing and printing. See master, 4.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• abbreviation An abbreviation of mister, a title used before the surname in theory, though not generally in practice, above some undefined social level, too old to be addressed as “Master”, not a knight or of some higher rank, and, in Britain though not in the United States, not entitled to be addressed as “Dr.”.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a form of address for a man
• noun a form of address for a man