[n] shortening something by omitting parts of it
[n] a shortened form of a word or phrase
\Ab*bre`vi*a"tion\, n. [LL. abbreviatio: cf. F. abbr['e]viation.]
1. The act of shortening, or reducing.
2. The result of abbreviating; an abridgment. --Tylor.
3. 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.
4. (Mus.) One dash, or more, through the stem of a note, dividing it respectively into quavers, semiquavers, or demi-semiquavers. --Moore.