Source : Webster's Revised Unabridged Dictionary (1913)

Unipolar \U`ni*po"lar\, a. [Uni- + polar.]
   1. (Physics) Having, or acting by means of, one pole only.

   2. (Anat.) Having but one pole or process; -- applied to
      those ganglionic nerve cells which have but one radiating
      process; -- opposed to multipolar.

   {Unipolar induction} (Elec.), induction, as in a conducting
      circuit, by only one pole of a magnet.

   {Unipolar stimulation} (Physiol.), the simulation sometimes
      produced when one electrode of an induction apparatus is
      applied to a nerve; -- called also {unipolar induction
      action}. --Du Bois-Reymond.

Source : WordNet®

unipolar
     adj : having a single pole [ant: {bipolar}]