collision course

collision course (plural collision courses)

1. A course or path between two or more objects which, if continued at the current rate, will result in a collision.

   The two boats were on a collision course, so they both veered starboard.

   • 2017 July 23, Brandon Nowalk, “The great game begins with a bang on Game Of Thrones (newbies)”, in The Onion AV Club‎:

     Now that everyone’s on the same continent, more or less, and everyone’s on collision courses, an episode can more naturally flow back and forth.

• on a collision course