unprecedented

[uhn-pres-i-den-tid]
adjective
  1. without previous instance; never before known or experienced; unexampled or unparalleled: an unprecedented event.

Origin of unprecedented

First recorded in 1615–25; un-1 + precedent + -ed2
Related formsun·prec·e·dent·ed·ly, adverbun·prec·e·dent·ed·ness, noun

Synonyms for unprecedented

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for unprecedentedness

unprecedented

adjective
  1. having no precedent; unparalleled
Derived Formsunprecedentedly, 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 unprecedentedness

unprecedented

adj.

1620s, from un- (1) "not" + precedented. In common use from c.1760.

Online Etymology Dictionary, © 2010 Douglas Harper