What does "mushroom" mean?

Additional senses

1. 2.Of or pertaining to mushrooms; as, mushroom catchup.
2. 3.Resembling mushrooms in rapidity of growth and shortness of duration; short-lived; ephemerial; as, mushroom cities. Mushroom anchor, an anchor shaped like a mushroom, capable of grasping the ground in whatever way it falls. -- Mushroom coral (Zoöl.), any coral of the genus Fungia. See Fungia. -- Mushroom spawn (Bot.), the mycelium, or primary filamentous growth, of the mushroom; also, cakes of earth and manure containing this growth, which are used for propagation of the mushroom.