narrowboat vs narrow boat

narrowboat and narrow boat both are nouns.

Word	Noun	Adjective	Verb	Adverb
narrowboat	Yes	No	No	No
narrow boat	Yes	No	No	No

As nouns, narrowboat and narrow boat are synonyms defined as:

narrowboat and narrow boat: a long boat that carries freight and is narrow enough to be used in canals

Other synonyms of narrowboat include canal boat.

narrowboat (noun)	narrow boat (noun)
a long boat that carries freight and is narrow enough to be used in canals	a long boat that carries freight and is narrow enough to be used in canals