Real Dictionary

takeoff
A takeoff of someone is a humorous imitation of the way in which they behave.
uncountable noun: Takeoff is the point in the development of something, such as an economy or a business, when it begins to be successful.
variable noun: Takeoff is the beginning of a flight, when an aircraft leaves the ground.

takeoff in American English
the act of leaving the ground from any angle, as in jumping, launching, or flight
noun: a taking or setting off; the leaving of the ground, as in leaping or in beginning a flight in an airplane

takeoff in British English
noun: the act or an instance of a plane leaving the ground and beginning to fly