Which of the following accurately describes engine displacement?

Engine displacement refers to the total volume of all the cylinders in an engine, which is essentially the total volume swept by the pistons as they move between their highest and lowest positions. This measurement is crucial as it directly impacts the engine's power output and efficiency.

Displacement is usually measured in liters (L) or cubic centimeters (cc) and is significant in determining the engine's capability and performance characteristics. A larger displacement typically allows for a greater air and fuel mixture to enter the engine, which results in increased power production.

The other options, while related to engine performance, do not define displacement. Mean effective pressure is an average pressure in the cylinder during the power stroke, which helps in calculating engine torque but does not represent the physical size of the engine. Peak horsepower and peak torque refer to performance metrics achieved at specific RPM ranges, which are influenced by displacement but are not descriptors of it.