Plain English Meaning
A specific model of small aircraft engine made by the Lycoming company. It has four cylinders arranged flat and opposite each other, uses fuel injection instead of a carburetor, and is about 360 cubic inches in size. You'll find it in many common training and personal aircraft.
Full Definition
A four-cylinder, horizontally opposed, fuel-injected aircraft piston engine manufactured by Lycoming, with a displacement of approximately 360 cubic inches. It is widely used in single-engine general aviation aircraft and typically produces between 180 and 210 horsepower depending on the variant.