Source : Free On-Line Dictionary of Computing

priority interrupt
     
        [hardware] Describes any stimulus compelling enough to yank
        one right out of {hack mode}.  Classically used to describe
        being dragged away by an {SO} for immediate sex, but may also
        refer to more mundane interruptions such as a fire alarm going
        off in the near vicinity.  Also called an {NMI} (non-maskable
        interrupt), especially in PC-land.
     
        [{Jargon File}]