tesla coil

from WordNet (r) 3.0 (2006)

Tesla coil
    n 1: a step-up transformer with an air core; used to produce
         high voltages at high frequencies

from The Collaborative International Dictionary of English v.0.48

Tesla coil \Tes"la coil\, Tesla transformer \Tes"la
trans*form"er\ [After N. Tesla, American electrician.] (Elec.)
   A transformer without iron, for high frequency alternating or
   oscillating currents; an oscillation transformer.
   [Webster 1913 Suppl.]