NMI

from Jargon File (4.4.4, 14 Aug 2003)

NMI
 /N.M.I/, n.

   Non-Maskable Interrupt. An IRQ 7 on the {PDP-11} or 680[01234]0; the
   NMI line on an 80[1234]86. In contrast with a {priority interrupt}
   (which might be ignored, although that is unlikely), an NMI is never
   ignored. Except, that is, on {clone} boxes, where NMI is often ignored
   on the motherboard because flaky hardware can generate many spurious
   ones.

from The Free On-line Dictionary of Computing (8 July 2008)

Non-Maskable Interrupt
NMI

   (NMI) An IRQ 7 on the {PDP-11} or {680x0} or the NMI line on
   an 80x86.  In contrast with a {priority interrupt} (which
   might be ignored, although that is unlikely), an NMI is
   *never* ignored.

   (1994-12-13)

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

NMI
       Non-Maskable Interrupt

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