Also, next door. to, at, or in the next house on the street, especially if it is very close by, or the adjacent apartment, office, room, or the like:
Go next-door and get your sister. Your sister is next-door. Her brother lives next-door.
adjective
2.
being situated or living next-door:
next-door neighbors.
Origin
1475-85
British Dictionary definitions for next door
next door
adjective, adverb (next-door when prenominal)
1.
at, in, or to the adjacent house, flat, building, etc: we live next door to the dentist, the next-door house
Word Origin and History for next door
next-door
adv.
also nextdoor, 1570s, from noun phrase next door "nearest house" (late 15c.), from next + door. Noun meaning "the people living next door" is from 1855.