The Collaborative International Dictionary of English v.0.48:

Trap \Trap\, n. [OE. trappe, AS. treppe; akin to OD. trappe,
   OHG. trapo; probably fr. the root of E. tramp, as that which
   is trod upon: cf. F. trappe, which is trod upon: cf. F.
   trappe, which perhaps influenced the English word.]
   1. A machine or contrivance that shuts suddenly, as with a
      spring, used for taking game or other animals; as, a trap
      for foxes.
      [1913 Webster]

            She would weep if that she saw a mouse
            Caught in a trap.                     --Chaucer.
      [1913 Webster]

   2. Fig.: A snare; an ambush; a stratagem; any device by which
      one may be caught unawares.
      [1913 Webster]

            Let their table be made a snare and a trap. --Rom.
                                                  xi. 9.
      [1913 Webster]

            God and your majesty
            Protect mine innocence, or I fall into
            The trap is laid for me!              --Shak.
      [1913 Webster]

   3. A wooden instrument shaped somewhat like a shoe, used in
      the game of trapball. It consists of a pivoted arm on one
      end of which is placed the ball to be thrown into the air
      by striking the other end. Also, a machine for throwing
      into the air glass balls, clay pigeons, etc., to be shot
      at.
      [1913 Webster]

   4. The game of trapball.
      [1913 Webster]

   5. A bend, sag, or partitioned chamber, in a drain, soil
      pipe, sewer, etc., arranged so that the liquid contents
      form a seal which prevents passage of air or gas, but
      permits the flow of liquids.
      [1913 Webster]

   6. A place in a water pipe, pump, etc., where air accumulates
      for want of an outlet.
      [1913 Webster]

   7. A wagon, or other vehicle. [Colloq.] --Thackeray.
      [1913 Webster]

   8. A kind of movable stepladder. --Knight.
      [1913 Webster]

   Trap stairs, a staircase leading to a trapdoor.

   Trap tree (Bot.) the jack; -- so called because it
      furnishes a kind of birdlime. See 1st Jack.
      [1913 Webster]