Definition 1 of 2
Definition
An Air Traffic Control authorization for an aircraft to depart from a specified runway. The clearance applies only to the aircraft addressed, only from the runway specified, and only at the time it is issued. It does not authorize taxi onto the runway by any other aircraft, and it remains valid only until the aircraft begins its takeoff roll or the controller cancels it.
Plain English
The tower controller has given you permission to start your takeoff roll on the runway they named. It is for you, on that runway, right now.
Context Anchor
Heard on the radio at a tower-controlled airport when an aircraft is ready to depart.
Derivation
Cleared comes from an older meaning of clear: open, free, or unobstructed. In aviation radio use, it also means authorized by air traffic control. Takeoff simply means the aircraft’s departure from the ground into flight.
Why Pilots Care
It establishes legal and operational separation from other traffic; acting without it risks collision or regulatory violation.
Intuition Check
Cleared does not mean the pilot personally sees that everything looks clear. Here, cleared means air traffic control has authorized the takeoff.
Example Sentence 1
Tower called, 'Cessna Three-Four-Alpha, runway two-seven, cleared for takeoff,' and the pilot read the clearance back before adding power.
Example Sentence 2
After the clearance the pilot advanced the throttle and began the takeoff roll.