auxiliary engine vs donkey engine

auxiliary engine and donkey engine both are nouns.

Word	Noun	Adjective	Verb	Adverb
auxiliary engine	Yes	No	No	No
donkey engine	Yes	No	No	No

As nouns, auxiliary engine and donkey engine are synonyms defined as:

auxiliary engine and donkey engine: (nautical) a small engine (as one used on board ships to operate a windlass)

auxiliary engine (noun)	donkey engine (noun)
(nautical) a small engine (as one used on board ships to operate a windlass)	(nautical) a small engine (as one used on board ships to operate a windlass)
	a locomotive for switching rolling stock in a railroad yard