• synonyms


[uhn-fas-uh n, -fah-suh n]
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verb (used with object)
  1. to release from or as from fastenings; detach.
  2. to undo or open (something fastened).
verb (used without object)
  1. to become unfastened.

Origin of unfasten

First recorded in 1175–1225, unfasten is from the Middle English word unfastnen. See un-2, fasten
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for unfasten


  1. to undo, untie, or open or become undone, untied, or opened
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 unfasten


early 13c., from un- (2) + fasten. Related: Unfastened; unfastening.

Online Etymology Dictionary, © 2010 Douglas Harper