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unreasonable

[uhn-ree-zuh-nuh-buh l, -reez-nuh-]
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adjective
  1. not reasonable or rational; acting at variance with or contrary to reason; not guided by reason or sound judgment; irrational: an unreasonable person.
  2. not in accordance with practical realities, as attitude or behavior; inappropriate: His Bohemianism was an unreasonable way of life for one so rich.
  3. excessive, immoderate, or exorbitant; unconscionable: an unreasonable price; unreasonable demands.
  4. not having the faculty of reason.
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Origin of unreasonable

First recorded in 1300–50, unreasonable is from the Middle English word unresonabel. See un-1, reasonable
Related formsun·rea·son·a·ble·ness, nounun·rea·son·a·bly, adverb

Synonyms

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1, 2. senseless, foolish, silly. 2. preposterous, absurd, stupid, nonsensical. 3. extravagant.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for unreasonable

unreasonable

adjective
  1. immoderate; excessiveunreasonable demands
  2. refusing to listen to reason
  3. lacking reason or judgment
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Derived Formsunreasonableness, noununreasonably, adverb
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 unreasonable

adj.

mid-14c., from un- (1) "not" + reasonable. Related: Unreasonably.

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Online Etymology Dictionary, © 2010 Douglas Harper