The Collaborative International Dictionary of English v.0.48:

Socket \Sock"et\, n. [OE. soket, a dim. through OF. fr. L.
   soccus. See Sock a covering for the foot.]
   1. An opening into which anything is fitted; any hollow thing
      or place which receives and holds something else; as, the
      sockets of the teeth.
      [1913 Webster]

            His eyeballs in their hollow sockets sink. --Dryden.
      [1913 Webster]

   2. Especially, the hollow tube or place in which a candle is
      fixed in the candlestick.
      [1913 Webster]

   3. (Electricity) the receptacle of an electric lamp into
      which a light bulb is inserted, containing contacts to
      conduct electricity to the bulb.
      [PJC]

   4. (Electricity) the receptacle fixed in a wall and connected
      by conductive wiring to an electrical supply, containing
      contacts to conduct electricity, and into which the plug
      of an electrical device is inserted; -- called also a
      wall socket or outlet. The socket will typically have
      two or three contacts; if three, the third is connected to
      a ground for safety.
      [PJC]

            And in the sockets oily bubbles dance. --Dryden.
      [1913 Webster]

   Socket bolt (Mach.), a bolt that passes through a thimble
      that is placed between the parts connected by the bolt.

   Socket chisel. Same as Framing chisel. See under
      Framing.

   Socket pipe, a pipe with an expansion at one end to receive
      the end of a connecting pipe.

   Socket pole, a pole armed with iron fixed on by means of a
      socket, and used to propel boats, etc. [U.S.]

   Socket wrench, a wrench consisting of a socket at the end
      of a shank or rod, for turning a nut, bolthead, etc., in a
      narrow or deep recess.
      [1913 Webster]

WordNet (r) 3.0 (2006):

socket wrench
    n 1: a wrench with a handle onto which sockets of different
         sizes can be fitted