Wordnet 3.0
ADJECTIVE (3)
1. 
 of or relating to manic depressive illness; 
2. 
 of, pertaining to, or occurring in both polar regions; 
- Example: "the bipolar distribution of certain species"3. 
 having two poles; 
The Collaborative International Dictionary of English v.0.48:
Bipolar \Bi*po"lar\, a. [Pref. bi- + polar. Cf. Dipolar.]
   Doubly polar; having two poles; as, a bipolar cell or
   corpuscle.
   [1913 Webster]
WordNet (r) 3.0 (2006):
bipolar
    adj 1: of or relating to manic depressive illness
    2: of, pertaining to, or occurring in both polar regions; "the
       bipolar distribution of certain species"
    3: having two poles [ant: unipolar]
The Free On-line Dictionary of Computing (30 December 2018):
bipolar
   1.  See bipolar transistor.
   2.  In digital transmission, an electrical
   line signalling method where the mark value alternates between
   positive and negative polarities.
   See also AMI.
   (1995-03-02)