Definition
The moment during the takeoff roll when the airplane's wings produce enough lift to support its weight and the wheels leave the runway surface, transitioning the airplane from ground operation to flight.
Plain English
The instant the airplane stops rolling on the runway and starts flying. The wheels come off the ground and the airplane is now supported by the air rather than the pavement.
Context Anchor
You will see this term in takeoff procedures, especially when discussing when to let the airplane leave the surface and begin the initial climb.
Derivation
A straightforward compound of "lift" (the upward aerodynamic force from the wings) and "off" (away from the surface). The word literally describes what is happening: the airplane is being lifted off the ground.
Why Pilots Care
It is the moment control changes from ground steering to full aerodynamic control; improper pitch or speed at liftoff can cause settling back onto the runway or loss of directional control.
Grounding Statement
During liftoff, the airplane changes from rolling on the surface to flying through the air.
Intuition Check
Do not treat liftoff as the whole takeoff. Liftoff is one moment within the takeoff: the aircraft has left the surface, but the takeoff and initial climb are still in progress.
Example Sentence 1
After accelerating down the runway, the pilot eased back on the yoke and the airplane reached liftoff at about 60 knots.
Example Sentence 2
In a crosswind, the pilot applied aileron into the wind and kept the airplane aligned until liftoff to prevent drifting.