> Engine braking occurs when the retarding forces within an engine are used to slow down a motor vehicle, as opposed to using additional external braking mechanisms such as friction brakes or magnetic brakes.
> The term is often confused with several other types of braking, most notably compression-release braking or "jake braking" which uses a different mechanism.
But when you see a sign saying "no engine braking" it refers to the jake brake, not down-shifting in a car. (It's a long trademark story over the use of "jake")
> The term is often confused with several other types of braking, most notably compression-release braking or "jake braking" which uses a different mechanism.
https://en.m.wikipedia.org/wiki/Engine_braking