1. The state or fact of occupying the same relative position or area in space: It was a coincidence that Doug was sitting next to Zena at the theater.
2. A sequence of events that although accidental seems to have been planned or arranged: The car crash seemed to be the result of several coincidences; such as, the rain, slippery roads, and an unlighted section of the roadway.
3. An situation that might have been arranged although it was really a happenstance: When Jim attends Kate's birthday party, he wants it to look like a coincidence, even though he was carefully arranging it with her sons.

It was just by coincidence that the two ladies wore the same dress to the party.

4. A timing action of two things happening at the same time: Pete tried to create a coincidence in order to meet his girl friend in the park by walking down one path while she was walking down the same one but from a different direction.