Source : Webster's Revised Unabridged Dictionary (1913)

Plug \Plug\, v. t. [imp. & p. p. {Plugged}; p. pr. & vb. n.
   {Plugging}.]
   To stop with a plug; to make tight by stopping a hole.

Plugging \Plug"ging\, n.
   1. The act of stopping with a plug.

   2. The material of which a plug or stopple is made.

Source : WordNet®

plug
     n 1: blockage consisting of an object designed to fill a hole
          tightly [syn: {stopper}, {stopple}]
     2: a wad of something chewable as tobacco [syn: {chew}, {chaw},
         {cud}, {quid}, {wad}]
     3: blatant or sensational promotion [syn: {ballyhoo}, {hoopla},
         {hype}]
     4: electrical device that fits into the cylinder head of an
        internal-combustion engine and ignites the gas by means of
        an electric spark [syn: {spark plug}, {sparking plug}]
     5: an electrical device with two or three pins that is inserted
        in a socket to make an electrical connection [syn: {male
        plug}]
     6: an upright hydrant for drawing water to use in fighting a
        fire [syn: {fireplug}, {fire hydrant}]
     7: an old or over-worked horse [syn: {hack}, {jade}, {nag}]
     [also: {plugging}, {plugged}]

plug
     v 1: fill or close tightly with or as if with a plug; "plug the
          hole"; "stop up the leak" [syn: {stop up}, {secure}]
     2: persist in working hard; "Students must plug away at this
        problem" [syn: {plug away}]
     3: deliver a quick blow to; "he punched me in the stomach"
        [syn: {punch}]
     4: make a plug for; praise the qualities or in order to sell or
        promote
     [also: {plugging}, {plugged}]

plugging
     See {plug}