Plain English Meaning

The gentle leveling-off you do a few feet above the runway right before landing, so the airplane stops descending sharply and settles softly onto the wheels.

Full Definition

The transition maneuver flown just before touchdown in which the pilot smoothly changes the airplane's flight path from the descending approach attitude to a path nearly parallel to the runway, slowing the descent rate so the airplane settles gently onto the landing surface.

Context Anchor

You encounter roundout during landing practice, especially when learning how to judge height above the runway and begin the final landing motion at the right time.