happening by or resulting from coincidence; by chance: a coincidental meeting.
existing or occurring at the same time.
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Origin of coincidental
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
of or happening by a coincidence; fortuitous
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
Online Etymology Dictionary, © 2010 Douglas Harper