Plain English Meaning
Loading the airplane with more weight than it is approved to carry, or placing the load in a way the aircraft is not approved to handle.
Full Definition
Operating an aircraft with a total weight that exceeds the maximum gross weight limit established by the manufacturer, or with weight distribution that exceeds any structural or center-of-gravity limit specified for that aircraft.
Context Anchor
Pilots encounter this during preflight planning, weight and balance checks, and decisions about passengers, baggage, and fuel.
Derivation
From 'over' (beyond, exceeding) and 'load' (the weight carried). In , the everyday sense of 'too much stuff' becomes a precise limit: exceeding any approved weight figure for that aircraft.