Broadly it could be called “a breach of driving etiquette.” If you are traveling straight in your lane at a steady speed, and somebody enters your right-of-way

Broadly it could be called “a breach of driving etiquette.” If you are traveling straight in your lane at a steady speed, and somebody enters your right-of-way and forces you to brake or steer away from your intended path, that person is said to have cut you off.