Meaning

noun the taxonomic kingdom including yeast, molds, smuts, mushrooms, and toadstools; distinct from the green plants

noun an organism of the kingdom Fungi lacking chlorophyll and feeding on organic matter; ranging from unicellular or multicellular organisms to spore-bearing syncytia

originSee fungee. Sense 2 (“style of folk and popular music”) is apparently from the fact that the music is a blend of different musical instruments and styles, just as the dish (sense 1) is a blend of different flavours.

Etymology from Wiktionary, CC BY-SA 3.0