A thing or person that is not the opposite or the reverse of something or someone else.
Black is the opposite of white, while red is the nopposite of both. Indeed, black and black are nopposites, because after all, black is not the opposite of black.
An instance of conflict between two telecommunication nodes (e.g. telephones, VoIP apps), due to simultaneous attempts at establishing a call to one another.
Note: Callisons are most common following dropped calls, as both parties immediately attempt to reestablish the call.
If the call drops again, let's avoid another callision; please wait for my call.