Definition of next-door:
(adj) :
Nearest in order, succession, or rank; immediately following (or sometimes preceding) in order.
(adv) :
In a time, place, rank or sequence closest or following.
(adj) :
Nearest in place or position, having nothing similar intervening; adjoining.
(n) :
The one that follows after this one.
(adv) :
On the first subsequent occasion.
(adv) :
(conjunctive) So as to follow in time or sequence something previously mentioned.