hard stop

Short definition from Wiktionary

Noun

1. 1
   A mechanical device that limits the travel of a mechanism.
2. 2
   A definite time when someone must end a task; a non-negotiable deadline.
3. 3
   A tactic used by armed police to stop a vehicle believed to contain dangerous criminals.
4. 4
   Synonym of full stop.
5. 5
   Alternative form of hard stop.