Source : Webster's Revised Unabridged Dictionary (1913)

Rap \Rap\, v. i. [imp. & p. p. {Rapped}; p. pr. & vb. n.
   {Rapping}.] [Akin to Sw. rappa to strike, rapp stroke, Dan.
   rap, perhaps of imitative origin.]
   To strike with a quick, sharp blow; to knock; as, to rap on
   the door.

Rap \Rap\, v. t. [imp. & p. p. {Rapped}, usually written {Rapt};
   p. pr. & vb. n. {Rapping}.] [OE. rapen; akin to LG. & D.
   rapen to snatch, G. raffen, Sw. rappa; cf. Dan. rappe sig to
   make haste, and Icel. hrapa to fall, to rush, hurry. The word
   has been confused with L. rapere to seize. Cf. {Rape}
   robbery, {Rapture}, {Raff}, v., {Ramp}, v.]
   1. To snatch away; to seize and hurry off.

            And through the Greeks and Ilians they rapt The
            whirring chariot.                     --Chapman.

            From Oxford I was rapt by my nephew, Sir Edmund
            Bacon, to Redgrove.                   --Sir H.
                                                  Wotton.

   2. To hasten. [Obs.] --Piers Plowman.

   3. To seize and bear away, as the mind or thoughts; to
      transport out of one's self; to affect with ecstasy or
      rapture; as, rapt into admiration.

            I'm rapt with joy to see my Marcia's tears.
                                                  --Addison.

            Rapt into future times, the bard begun. --Pope.

   4. To exchange; to truck. [Obs. & Law]

   {To rap and ren}, {To rap and rend}. [Perhaps fr. Icel. hrapa
      to hurry and r[ae]na plunder, fr. r[=a]n plunder, E. ran.]
      To seize and plunder; to snatch by violence. --Dryden.
      ``[Ye] waste all that ye may rape and renne.'' --Chaucer.

            All they could rap and rend pilfer.   --Hudibras.

   {To rap out}, to utter with sudden violence, as an oath.

            A judge who rapped out a great oath.  --Addison.

Source : WordNet®

rap
     n 1: a reproach for some lapse or misdeed; "he took the blame for
          it"; "it was a bum rap" [syn: {blame}]
     2: a gentle blow [syn: {strike}, {tap}]
     3: the sound made by a gentle blow [syn: {pat}, {tap}]
     4: voluble conversation
     5: genre of African-American music of the 1980s and 1990s in
        which rhyming lyrics are chanted to a musical
        accompaniment; several forms of rap have emerged [syn: {rap
        music}, {hip-hop}]
     6: the act of hitting vigorously; "he gave the table a whack"
        [syn: {knock}, {belt}, {whack}, {whang}]
     [also: {rapping}, {rapped}]

rap
     v 1: strike sharply; "rap him on the knuckles" [syn: {knap}]
     2: make light, repeated taps on a surface; "he was tapping his
        fingers on the table impatiently" [syn: {tap}, {knock}, {pink}]
     3: perform rap music
     4: talk volubly
     [also: {rapping}, {rapped}]

rapping
     See {rap}