abbreviation

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

• noun The act or product of shortening.
• noun A shortened form of a word or phrase used chiefly in writing to represent the complete form, such as Mass. for Massachusetts or USMC for United States Marine Corps.

from The Century Dictionary.

• noun ;
• noun The act of abbreviating, shortening, or contracting; the state of being abbreviated; abridgment.
• noun A shortened or contracted form; a part used for the whole.
• noun In mathematics, a reduction of fractions to the lowest terms.
• noun In music, a method of notation by means of which certain repeated notes, chords, or passages are indicated without being written out in full.

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

• noun The act of shortening, or reducing.
• noun The result of abbreviating; an abridgment.
• noun The form to which a word or phrase is reduced by contraction and omission; a letter or letters, standing for a word or phrase of which they are a part; as, Gen. for Genesis; U.S.A. for United States of America.
• noun (Mus.) One dash, or more, through the stem of a note, dividing it respectively into quavers, semiquavers, or demi-semiquavers.

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

• noun music A notation used in music score to denote a direction, as pp or mf.
• noun music One or more dashes through the stem of a note, dividing it respectively into quavers, semiquavers, demisemiquavers, or hemidemisemiquavers.
• noun Any convenient short form used as a substitutuion for an understood or inferred whole.
• noun biology Loss during evolution of the final stages of the ancestral ontogenetic pattern.
• noun mathematics Reduction to lower terms, as a fraction.

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

• noun a shortened form of a word or phrase
• noun shortening something by omitting parts of it