WordNet (r) 3.0 (2006):

DMZ
    n 1: a zone from which military forces or operations or
         installations are prohibited; "tensions exist on both sides
         of the demilitarized zone separating North Korea and South
         Korea" [syn: demilitarized zone, DMZ]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

DMZ
       DeMilitarized Zone (LAN, Internet)


The Jargon File (version 4.4.7, 29 Dec 2003):

DMZ


    [common] Literally, De-Militarized Zone. Figuratively, the portion of a
    private network that is visible through the network's firewalls (see 
    firewall machine). Coined in the late 1990s as jargon, this term is now
    borderline techspeak.


The Free On-line Dictionary of Computing (30 December 2018):

De-Militarised Zone
DMZ

    (DMZ) (From the military term for an area between
   two opponents where fighting is prevented) DMZ Ethernets
   connect networks and computers controlled by different bodies.
   They may be external or internal.  External DMZ Ethernets link
   regional networks with routers to internal networks.
   Internal DMZ Ethernets link local nodes with routers to the
   regional networks.

   Compare red zone.

   (1995-02-23)