adverb , adjective , noun
■ adverb
in the next room, house or building :
The cat is from the house next door.
The manager's office is just next door.
We live next door to the bank.
► ˌnext-ˈdoor adjective [ only before noun ]:
our next-door neighbours
the next-door house
■ noun
[ U+sing./pl. v . ] ( BrE , informal ) the people who live in the house or flat / apartment next to yours :
Is that next door's dog?