To physically separate or isolate a system from other systems or networks (verb).
To physically separate or isolate a system from other systems or networks (verb).
The physical separation or isolation of a system from other systems or networks (noun).
An interface between two systems at which (a) they are not connected physically and (b) any logical connection is not automated (i.e., data is transferred through the interface only manually, under human control). (See: sneaker net. Compare: gateway.)
Example: Computer A and computer B are on opposite sides of a room. To move data from A to B, a person carries a disk across the room. If A and B operate in different security domains, then moving data across the air gap may involve an upgrade or downgrade operation.