- A time or date on or before which something must be completed.
- (archaic) A guideline marked on a plate for a printing press inside which all content must appear.
- (archaic) A line that does not move.
- (archaic) A boundary around a prison, which if crossed the prisoner would be shot.
- A fixed time or date (which may be moved) before which something must be completed (or appropriate excuse be presented) and which if you cross will result in your demise (most likely not physical though this cannot be guaranteed)