Definition
An ATC authorization for an aircraft to depart. It is issued by the controller responsible for the runway and grants the pilot permission to begin the takeoff roll on the specified runway under the conditions stated in the clearance.
Plain English
The controller is telling you that you may now take off from the runway they have named. Until you hear these exact words, you are not permitted to start your takeoff roll.
Context Anchor
Heard on the radio at a towered airport when an aircraft is waiting to depart from a runway.
Derivation
Cleared comes from the idea of making a path clear or free from obstruction. In air traffic control language, it means permission has been given for a specific action, in this case beginning the takeoff.
Why Pilots Care
Departing without this clearance risks collision with other aircraft or vehicles and violates federal regulations.
Intuition Check
Do not read “cleared” as “guaranteed safe in every way.” Here it means “authorized by air traffic control based on known traffic and known conditions.”
Example Sentence 1
Tower called, 'Cessna Three Four Tango, runway two seven, cleared for takeoff,' and the pilot read back the clearance before advancing the throttle.
Example Sentence 2
After completing the engine run-up the pilot waited until receiving clearance before taxiing onto the runway.