See more synonyms for unthinking on Thesaurus.com
  1. thoughtless; heedless; inconsiderate: an unthinking, tactless person.
  2. indicating lack of thought or reflection: a dull, unthinking expression on his face.
  3. not endowed with the faculty of thought: unthinking matter.
  4. not exercising thought; not given to reflection: This book will not profit an unthinking person.
  5. not thinking; unmindful: chores done in an unthinking manner.

Origin of unthinking

First recorded in 1670–80; un-1 + thinking
Related formsun·think·ing·ly, adverbun·think·ing·ness, noun


verb (used without object), un·thought, un·think·ing.
  1. to end one's thought or reverse the process of thought.
verb (used with object), un·thought, un·think·ing.
  1. to dispel from the mind: Unthink your thoughts.

Origin of unthink

First recorded in 1590–1600; un-2 + think1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for unthinking


  1. lacking thoughtfulness; inconsiderate
  2. heedless; inadvertentit was done in an unthinking moment
  3. not thinking or able to think
Derived Formsunthinkingly, adverbunthinkingness, noun


verb -thinks, -thinking or -thought (tr)
  1. to reverse one's opinion about
  2. to dispel from the mind
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 unthinking

"unreflecting," 1670s, from un- + present participle of think.

Online Etymology Dictionary, © 2010 Douglas Harper