The Collaborative International Dictionary of English v.0.48:

Transformer \Trans*form"er\, n.
   1. One who, or that which, transforms. Specif. (Elec.), an
      apparatus for producing from a given electrical current
      another current of different voltage.
      [1913 Webster]

   2. (1990's) a toy consisting of a figure or representation of
      an object, constructed of interlocking parts in such a way
      that a series of turning or twisting motions of the parts
      can transform the object from one type of object to a
      different type of object, such as from an animal to an
      automobile.
      [PJC]

   Multiple transformer. (Elec.)
      (a) A transformer connected in multiple or in parallel
          with the primary circuit.
      (b) A transformer with more than one primary or more than
          one secondary coil.

   Parallel transformer (Elec.), a transformer connected in
      parallel.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

transformer
    n 1: an electrical device by which alternating current of one
         voltage is changed to another voltage

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "transformer":
   agent, alembic, alterant, alterative, alterer, anvil, caldron,
   catalyst, catalytic agent, crucible, engine, ferment,
   innovationist, innovator, introducer, lathe, leaven, machine,
   melting pot, modificator, modifier, mortar, motor, precursor,
   retort, test tube, transducer, transmogrifier, yeast