Plain English Meaning
The steady speed an airplane is flown at once it has finished climbing and is travelling level toward its destination.
Full Definition
The airspeed at which an airplane is flown during the cruise phase of flight, typically a manufacturer-recommended setting that balances speed, fuel efficiency, and engine wear for level flight at a chosen altitude and power setting.
Context Anchor
Seen when the Airplane Flying Handbook explains how to begin a climb from normal cruise flight.
Derivation
Cruise' comes from the Dutch 'kruisen,' meaning to cross or sail back and forth. In aviation it carries the same idea as in sailing: the steady, settled of travel between and , after the of climbing is done.