1. Relating to or having two poles or charges.

2. Relating to a device capable of using two polarizations, such as a transistor that uses positive and negative charge carriers.

3. Relating to or involving both of the earth's polar regions.

4. Having two opposite or contradictory ideas or natures: the bipolar world of the postwar period.

5. Biology Having two poles or opposite extremities: a bipolar neuron.

6. Psychiatry Of, relating to, or having bipolar disorder.