unneighborly vs unneighbourly

unneighborly and unneighbourly both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unneighborly	No	Yes	No	No
unneighbourly	No	Yes	No	No

As adjectives, unneighborly and unneighbourly are synonyms defined as:

unneighborly and unneighbourly: not exhibiting the qualities expected in a friendly neighbor

unneighborly (adjective)	unneighbourly (adjective)
not exhibiting the qualities expected in a friendly neighbor	not exhibiting the qualities expected in a friendly neighbor