WordNet (r) 3.0 (2006):

diode
    n 1: a thermionic tube having two electrodes; used as a
         rectifier [syn: diode, rectifying tube, rectifying
         valve]
    2: a semiconductor that consists of a p-n junction [syn:
       diode, semiconductor diode, junction rectifier,
       crystal rectifier]

The Free On-line Dictionary of Computing (30 December 2018):

diode

    A semiconductor device which
   conducts electric current run in one direction only.  This is
   the simplest kind of semiconductor device, it has two
   terminals and a single PN junction.  One diode can be used as
   a half-wave rectifier or four as a full-wave rectifier.

   (1995-03-14)