ATPL - A "slat" is:

Question id 48 - Principles of Flight - ATPL - Airline Transport Pilot license

A leading edge high lift device, hinged at its forward edge, which increases the camber and leading edge radius of the main aerofoil when deployed.

A trailing edge device which is automatically deployed by movement of the stagnation point at high angles of attack.

An auxiliary, cambered aerofoil positioned forward of the main aerofoil so as to form a slot.

A fixed slot in the leading edge of some older types of aircraft.