coinciding coin·ci·ding US/ˌkoʊʌˈnsaɪdɪŋ/ uncommon adjective 1. occurring or operating at the same time “a series of coincident events” Synonymscoincidentcoincidentalconcurrentcooccurringsimultaneous Similarsynchronous 2. matching point for point “coincident circles” Synonymscoincident Similarcongruent WordNet 2.1 (Princeton University). CMU Pronouncing Dictionary. WordNet 2.1 Copyright Princeton University. All rights reserved.