mushroom
1. mush.room \'m*sh-.ru:m, -.ru.m\ n [ME musseroun, fr. MF mousseron, fr. LL mussirion-, mussir] often attrib io 1a: an enlarged complex aerial fleshy fruiting body of a fungus (as of the class Basidiomycetes) that consists typically of a stem bearing a flattened cap; esp : one that is edible 1b: FUNGUS archaic 2: UPSTART 3: something resembling a mushroom 2. mushroom vi 1: to spring up suddenly or multiply rapidly of a bullet 2a: to flatten at the end at impact 2b: to well up and spread out laterally from a central source
Webster's English Dictionary