Plain English Meaning
The flaps are stuck and will not move. The pilot has to land the airplane without being able to use them.
Full Definition
An abnormal condition in which the wing flaps cannot be extended or retracted at all, leaving them stuck in their current position (typically fully retracted) due to a mechanical, electrical, or hydraulic failure of the flap system.
Context Anchor
Encountered during abnormal landing procedures, especially when the pilot selects flaps on approach and they do not extend.
Derivation
“Flap” originally referred to a loose or hinged piece that moves. In an airplane, flaps are hinged surfaces on the back of the wings. “Total” means the problem affects the flap system as a whole, not just one small part of it.