multiengine plane vs multiengine airplane

multiengine plane and multiengine airplane both are nouns.

Word	Noun	Adjective	Verb	Adverb
multiengine plane	Yes	No	No	No
multiengine airplane	Yes	No	No	No

As nouns, multiengine plane and multiengine airplane are synonyms defined as:

multiengine plane and multiengine airplane: a plane with two or more engines

multiengine plane (noun)	multiengine airplane (noun)
a plane with two or more engines	a plane with two or more engines