Plain English Meaning

Stopping the climb (or descent) and flying straight at the altitude you wanted to reach.

Full Definition

The transition from a climb or descent to straight-and-level flight at a chosen altitude, accomplished by smoothly adjusting pitch attitude and power so the airplane stops gaining or losing altitude and maintains the target altitude at cruise airspeed.

Context Anchor

Encountered when ending a climb after takeoff, during a practice maneuver, or when reaching an assigned altitude from air traffic control.

Derivation

From 'level' (flat, even) plus '' (away from the previous action). is moving 'off' the climb or descent and onto .