Fouls (3.C): It is the responsibility of all players to avoid contact in every way possible.
Avoid contact in every way reasonably possible, while still playing ultimate. Some contact is inevitable, but players have an affirmative obligation to make reasonable efforts to avoid contact.
Dangerous Play. Actions demonstrating reckless disregard for the safety of or posing a significant risk of injury to fellow players, or other dangerously aggressive behavior are considered "dangerous play" and are treated as a foul. The proper call in such circumstances is "dangerous play" and play stops. This rule is not superseded by any other rule.
The following are non-exhaustive examples of dangerous play:
Resolution. If uncontested, a call of "dangerous play" is resolved as an analogous foul (e.g., if the call occurred while or immediately after the calling player was making a play on a disc in the air, it is treated as a Receiving Foul (17.I.4.b)). A player called for dangerous play may contest the call if they believe the call was incorrect (17.B).
Dangerous play between a thrower and marker is treated as a throwing foul that affected the play, regardless of whether or when the disc is released or when contact occurs, unless the calling player determines otherwise.