Plain English Meaning
A measurement, in inches, of how far behind the airplane's chosen starting point an item or station sits. Anything behind the starting line is recorded as a positive number; anything in front of it is recorded as a negative number.
Full Definition
In weight and balance calculations, a station or arm measured in inches aft (rearward) of the reference datum, expressed as a positive number. Distances forward of the datum are expressed as negative inches.
Context Anchor
Seen in aircraft weight and balance data when listing the location of seats, fuel, baggage, or equipment relative to the datum.