/ kəʊˌɪnsɪˈdentl; NAmE koʊ-/ adjective
[ not usually before noun ] happening by chance; not planned :
I suppose your presence here today is not entirely coincidental .
It's purely coincidental that we both chose to call our daughters Emma.
► co·in·ci·den·tal·ly / -təli; NAmE / adverb :
Coincidentally, they had both studied in Paris.