1. the state of being in the middle of or between two factors or conditions or midway on some scale.

2. (pl. media) any means or agency through which messages are transmitted or information is diffused (e.g., the medium of television).

3. (pl. media) a substance, such as air or water, that serves to transmit a physical effect, such as sound or light.

4. (pl. media) a nutritive substance in which molds or other organisms are grown in a laboratory.

5. in spiritualism, a person who functions as the instrument of alleged communication between the living and the dead. Some mediums often claim paranormal abilities, such as clairvoyance, astral projection, or powers of psychic healing.