bipolar

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Relating to or having two poles or charges.
• adjective Relating to a device capable of using two polarizations, such as a transistor that uses positive and negative charge carriers.
• adjective Relating to or involving both of the earth's polar regions.
• adjective Having two opposite or contradictory ideas or natures.
• adjective Biology Having two poles or opposite extremities.
• adjective Psychiatry Of or relating to bipolar disorder.

from The Century Dictionary.

• Doubly polar; having two poles.
• Specifically In anatomy, having two processes from opposite poles: said of certain nervecells.
• In electricity, pertaining to an electric machine having two poles.
• In zoology, occurring in the north and south polar regions, but not in the intervening tropical ocean. See extract under bipolarity, 2.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Doubly polar; having two poles.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Involving both extremes (poles) at the same time.
• adjective Relating to or having bipolar disorder.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective of or relating to manic depressive illness
• adjective having two poles
• adjective of, pertaining to, or occurring in both polar regions