a person who lives next door, or very close, to one

Let's invite the neighbours round

a person next to one, or a country, etc next to one's own

chatting to one's dinner-party neighbour

our EU neighbours

archaic one's fellow human being

Love thy neighbour

literary or archaic to adjoin or lie near to (a place)

the Jewish quarter that neighbours Old Town Square

dated to be neighbours

We neighboured in our youth

literary (+ on/upon) to adjoin somewhere