neighboring vs neighbouring

neighboring and neighbouring both are adjectives.

Word	Noun	Adjective	Verb	Adverb
neighboring	No	Yes	No	No
neighbouring	No	Yes	No	No

As adjectives, neighboring and neighbouring are synonyms defined as:

neighboring and neighbouring: having a common boundary or edge; abutting; touching

Other synonyms of neighboring include adjacent, conterminous, contiguous.

neighboring (adjective)	neighbouring (adjective)
having a common boundary or edge; abutting; touching	having a common boundary or edge; abutting; touching