Plain English Meaning
A helicopter (or similar rotor aircraft) powered by a jet-style turbine engine instead of a piston engine like the kind found in a small airplane or car.
Full Definition
A rotary-wing aircraft, such as a helicopter, in which the main rotor and tail rotor are driven by one or more gas turbine engines rather than by a piston (reciprocating) engine.
Context Anchor
Seen in aircraft inspection requirements, especially when deciding which inspection program applies to a rotorcraft used in civil operations.
Derivation
Turbine comes from the Latin turbo, meaning a spinning thing or whirl. Rotorcraft simply means an aircraft that gets its from blades. Put together, the term describes a rotor-lifted aircraft whose blades are spun by a turbine engine.