Definition of "air-gap" []

• In electricity, the opening or space between the poles of a magnet or between the armatures and pole-pieces of a dynamo or motor; that portion of a magnetic circuit which contains no iron; the space between the terminals of an electrostatic machine, induction-coil, or discharger. (noun)

The Century Dictionary (Public Domain)

• "The fed. gov demanded opening up the transmission market for competitive access, which led to previously closed, air-gap security, networks being made much more vulnerable through connection to other networks."
• "The commenter says things I agree with, notably that electric utilities should take well-known measures to improve security: (1) air-gap, to reduce the attack surface; (2) reduce buffer overflows and other well-known vulnerabilities."
• "The fed.gov demanded opening up the transmission market for competitive access, which led to previously closed, air-gap security, networks being made much more vulnerable through connection to other networks."