Source : Webster's Revised Unabridged Dictionary (1913)

Plug \Plug\, n. [Akin to D. plug, G. pflock, Dan. pl["o]k, plug,
   Sw. plugg; cf. W. ploc.]
   1. Any piece of wood, metal, or other substance used to stop
      or fill a hole; a stopple.

   2. A flat oblong cake of pressed tobacco. [U. S.]

   3. A high, tapering silk hat. [Slang, U.S.]

   4. A worthless horse. [Slang, U.S.]

   5. (Building) A block of wood let into a wall, to afford a
      hold for nails.

   {Fire plug}, a street hydrant to which hose may be attached.
      [U. S.]

   {Hawse plug} (Naut.), a plug to stop a hawse hole.

   {Plug and feather}. (Stone Working) See {Feather}, n., 7.

   {Plug centerbit}, a centerbit ending in a small cylinder
      instead of a point, so as to follow and enlarge a hole
      previously made, or to form a counterbore around it.

   {Plug rod} (Steam Eng.), a rod attached to the beam for
      working the valves, as in the Cornish engine.

   {Plug valve} (Mech.), a tapering valve, which turns in a case
      like the plug of a faucet.