Definitions
1.NounA time limit in the form of a date on or before which something must be completed."I must make this deadline or my boss will kill me!"
2.NounA guideline marked on a plate for a printing press.
3.NounA line that does not move. (Can we add an example for this sense?)
4.NounA boundary around a prison, prisoners crossing which would be shot.
5.VerbTo render an item non-mission-capable; to ground an aircraft, etc.