Trap

 TRAP 1. n. A program interrupt, usually used specifically to refer to
       an interrupt caused by some illegal action taking place in the user
       program. In most cases the system monitor performs some action related
       to the nature of the illegality, then returns control to the program.
       See UUO. 2. v. To cause a trap. "These instructions trap to the
       monitor." Also used transitively to indicate the cause of the
       trap. "The monitor traps all input/output instructions."