Source : Webster's Revised Unabridged Dictionary (1913)

Gag \Gag\, n.
   1. Something thrust into the mouth or throat to hinder
      speaking.

   2. A mouthful that makes one retch; a choking bit; as, a gag
      of mutton fat. --Lamb.

   3. A speech or phrase interpolated offhand by an actor on the
      stage in his part as written, usually consisting of some
      seasonable or local allusion. [Slang]

Gag \Gag\, v. t. [imp. & p. p. {Gagged}; p. pr. & vb. n.
   {Gagging}.] [Prob. fr. W. cegio to choke or strangle, fr. ceg
   mouth, opening, entrance.]
   1. To stop the mouth of, by thrusting sometimes in, so as to
      hinder speaking; hence, to silence by authority or by
      violence; not to allow freedom of speech to. --Marvell.

            The time was not yet come when eloquence was to be
            gagged, and reason to be hood winked. --Maccaulay.

   2. To pry or hold open by means of a gag.

            Mouths gagged to such a wideness.     --Fortescue
                                                  (Transl.).

   3. To cause to heave with nausea.

Gag \Gag\, v. i.
   1. To heave with nausea; to retch.

   2. To introduce gags or interpolations. See {Gag}, n., 3.
      [Slang] --Cornill Mag.

Source : WordNet®

gag
     v 1: prevent from speaking out; "The press was gagged" [syn: {muzzle}]
     2: be too tight; rub or press; "This neckband is choking the
        cat" [syn: {choke}, {fret}]
     3: tie a gag around someone's mouth in order to silence them;
        "The burglars gagged the home owner and tied him to a
        chair" [syn: {muzzle}]
     4: make jokes or quips; "The students were gagging during
        dinner" [syn: {quip}]
     5: struggle for breath; have insufficient oxygen intake; "he
        swallowed a fishbone and gagged" [syn: {choke}, {strangle},
         {suffocate}]
     6: cause to retch or choke [syn: {choke}]
     7: make an unsuccessful effort to vomit; strain to vomit [syn:
        {heave}, {retch}]
     [also: {gagging}, {gagged}]

gag
     n 1: a humorous anecdote or remark intended to provoke laughter;
          "he told a very funny joke"; "he knows a million gags";
          "thanks for the laugh"; "he laughed unpleasantly at
          hisown jest"; "even a schoolboy's jape is supposed to
          have some ascertainable point" [syn: {joke}, {laugh}, {jest},
           {jape}]
     2: restraint put into a person's mouth to prevent speaking or
        shouting [syn: {muzzle}]
     [also: {gagging}, {gagged}]

Source : Free On-Line Dictionary of Computing

gag
     
        Equivalent to {choke}, but connotes more disgust. "Hey, this
        is Fortran code.  No wonder the C compiler gagged."  See also
        {barf}.
     
        [{Jargon File}]