The Collaborative International Dictionary of English v.0.48:

colliding-beam machine \colliding-beam machine\ n. (Physics)
   a particle accelerator in which two separate beams of
   particles (usually of opposite charge) are circulated in
   opposite directions and directed so as to collide head on; --
   called also colliding-beam accelerator and collider.

   Note: This technique allows the production of collisions of
         higher energy than would be possible with a single beam
         produced by the same device.

   Syn: particle collider; colliding-beam accelerator; collider.
        [WordNet 1.5 +PJC]

The Collaborative International Dictionary of English v.0.48:

collider \col*lid"er\ n. (Physics)
   a particle accelerator in which two separate beams of
   particles (usually of opposite charge) are circulated in
   opposite directions and directed so as to collide head on.
   This technique allows the production of collisions of higher
   energy than would be possible with a single beam produced by
   the same device.

   Syn: particle collider; colliding-beam accelerator;
        colliding-beam machine. [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

collider
    n 1: an accelerator in which two beams of particles are forced
         to collide head on