1. One of numerable fungi mainly of the order Agaricales: An agaric is a fungus with a large cap resembling an umbrella with numerous radiating gills on the underside. Some types are edible and some are poisonous, like the fly agaric.

The fungi of the family Agaricaceae include the mushrooms.
2. The dried spore-producing elements of specific fungi: The agaric of the Polyphorus officinalis used to be employed in medicine.

A white, tasteless, odorless powder extracted from the fungus Polyporus officinalis: Agaric acid has been used to treat diarrhea, reduce bronchial secretions, and reduce night sweats.