1. (Bot.) Any one of the Fungi, a large and very complex group of thallophytes of low organization, -- the molds, mildews, rusts, smuts, mushrooms, toadstools, puff balls, and the allies of each. Note: The fungi are all destitute of chorophyll, and, therefore, to be supplied with elaborated nourishment, must live as saprophytes or parasites. They range in size from single micros...