Plain English Meaning

An airplane with more than one engine. Flying one requires extra training and a special rating because handling it (especially if an engine fails) is different from flying a single-engine airplane.

Full Definition

An aircraft powered by two or more engines. In pilot certification and training contexts, it specifically refers to airplanes with more than one engine, which require additional training and a separate class rating to operate as pilot in command.

Context Anchor

Seen in instrument training when discussing aircraft used for instruction, performance, and procedures that differ from single-engine aircraft.

Derivation

Multi- comes from Latin multus, meaning 'many.' Combined with engine, it simply means 'many engines'—but the aviation usage points to a specific of aircraft with its own rating and training requirements.