Definition
The round out (also called the flare) is the maneuver performed just before touchdown in which the pilot smoothly transitions the airplane from the descending approach attitude to a nose-slightly-high landing attitude, gradually reducing the rate of descent so the wheels meet the runway gently rather than at the full descent speed.
Plain English
It is the smooth, curved leveling-off the pilot makes a few feet above the runway, easing the nose up so the airplane stops descending sharply and settles softly onto its main wheels.
Context Anchor
You encounter round out during the final moments of a normal landing, after the approach and before the wheels touch the runway.
Derivation
From the everyday phrase 'to round something out' -- meaning to smooth a sharp corner into a curve. The descent path is sharp; the round out turns that sharp angle into a gentle curve that ends with the wheels touching the runway.
Why Pilots Care
Correct timing and height of the round out prevent hard landings, bounces, prop strikes, and runway excursions.
Intuition Check
Round out does not mean making a turn or flying in a circle. In landing, it means smoothly changing the airplane’s path from downward to nearly level just above the runway.
Example Sentence 1
About ten to twenty feet above the runway, the student began the round out by gradually easing back on the yoke to slow the descent.
Example Sentence 2
If the round out is started too high, the airplane may float down the runway and risk running out of available landing distance.