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adjective, rash·er, rash·est.
  1. acting or tending to act too hastily or without due consideration.
  2. characterized by or showing too great haste or lack of consideration: rash promises.
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Origin of rash1

1350–1400; Middle English; cognate with Dutch, German rasch quick, brisk, Old Norse rǫskr brave
Related formsrash·ly, adverbrash·ness, noun


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  1. an eruption or efflorescence on the skin.
  2. a multitude of instances of something occurring more or less during the same period of time: a rash of robberies last month.
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Origin of rash2

1700–10; < French rache (obsolete), Old French rasche skin eruption, derivative of raschier to scratch, ultimately < Latin rādere to scratch
Related formsrash·like, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for rash


  1. acting without due consideration or thought; impetuous
  2. characterized by or resulting from excessive haste or impetuositya rash word
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Derived Formsrashly, adverbrashness, noun

Word Origin

C14: from Old High German rasc hurried, clever; related to Old Norse roskr brave


  1. pathol any skin eruption
  2. a series of unpleasant and unexpected occurrencesa rash of forest fires
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Derived Formsrashlike, adjective

Word Origin

C18: from Old French rasche, from raschier to scratch, from Latin rādere to scrape
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for rash


late 14c., "nimble, quick, vigorous" (early 14c. as a surname), a Scottish and northern word, perhaps from Old English -ræsc (cf. ligræsc "flash of lightning") or one of its Germanic cognates, from Proto-Germanic *raskuz (cf. Middle Low German rasch, Middle Dutch rasc "quick, swift," German rasch "quick, fast"). Related to Old English horsc "quick-witted." Sense of "reckless, impetuous, heedless of consequences" is attested from c.1500. Related: Rashly; rashness.

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"eruption of small red spots on skin," 1709, perhaps from French rache "a sore" (Old French rasche "rash, scurf"), from Vulgar Latin *rasicare "to scrape" (also source of Old Provençal rascar, Spanish rascar "to scrape, scratch," Italian raschina "itch"), from Latin rasus "scraped," past participle of radere "to scrape" (see raze). The connecting notion would be of itching. Figurative sense of "any sudden outbreak or proliferation" first recorded 1820.

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Online Etymology Dictionary, © 2010 Douglas Harper

rash in Medicine


  1. A skin eruption.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.