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Meaning of gullywasher

gul•ly•wash•er

Pronunciation: (gul'ē wosh"ur, -wô"shur), [key]
— n. Chiefly Midland and Western U.S.
  1. a usually short, heavy rainstorm.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.