hard stop

noun4

1. •
   A mechanical device that limits the travel of a mechanism.
2. •
   A definite time when someone must end a task; a non-negotiable deadline.

   • I have a hard stop at 4 pm, so please try to cover everything in the meeting before then.
3. •
   A tactic used by armed police to stop a vehicle believed to contain dangerous criminals.
4. •
   Synonym of full stop.