From Longman Dictionary of Contemporary Englishcoincidentalco‧in‧ci‧den‧tal /kəʊˌɪnsəˈdentl $ koʊ-/ AWL adjective CHANCE/BY CHANCEhappening completely by chance without being planned → coincidencepurely/completely/entirely coincidental Any similarity between this film and real events is purely coincidental. —coincidentally adverb [sentence adverb] We have become profitable. Not coincidentally, we have only half as many employees as we did in 1988.
Examples from the Corpus
coincidental• Fourteen months later, a judge said the case against Harris was too coincidental.• Furthermore, the public is told that ail similarities to dolphins are purely coincidental.• His fierce pride demanded that she must assume their meeting had been coincidental.• I had come to believe that on the world stage little occurred that was strictly coincidental.• Such a concentration of comparable geometrical forms can not be coincidental.• These are then excreted and, should they prove to have a useful, coincidental effect, the bacteria thrive.• The link, however, could have been merely coincidental, he noted.purely/completely/entirely coincidental• Furthermore, the public is told that ail similarities to dolphins are purely coincidental. 