Plain English Meaning
A worksheet the pilot fills out before and during a flight to keep track of the route, the time, the fuel, and the radio settings, so nothing important is left to memory.
Full Definition
A written record prepared by the pilot for a specific flight that lists the planned route, checkpoints, headings, distances, estimated and actual times, fuel burn, altitudes, frequencies, and other operational data needed to navigate and monitor the flight from departure to destination.