Kinktionary
More like guidelines and a lot less like definitions.
Play Fighting
A playful form of fighting between two or more participants. Generally there is explicit content of what is allowed or not allowed during the "fight" negotiated before hand between people. This may include: scratching, biting, restraining holds, choking / breath play, pinching, grabbing of genitals, slapping, punching, hair pulling and many other possible ways to hurt and deter the other participant(s) to let go or give up.
Often the objective of this play is to make the other submit or surrender, however many do this for the enjoyment of the act of fighting and not to have the other person submit as quickly as possible. The submission or surrender may be caused by the exhaustion of a participant rather than through force, injury or something else.