From WordNet (r) 3.0 (2006) [wn]:
upstairs
adv 1: on a floor above; "they lived upstairs" [syn: upstairs,
up the stairs, on a higher floor] [ant: below,
down the stairs, downstairs, on a lower floor]
2: with respect to the mind; "she's a bit weak upstairs"
adj 1: on or of upper floors of a building; "the upstairs maid";
"an upstairs room" [syn: upstairs, upstair] [ant:
downstair, downstairs]
n 1: the part of a building above the ground floor; "no one was
allowed to see the upstairs"
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Upstairs \Up*stairs"\, adv.
Up the stairs; in or toward an upper story.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Upstairs \Up"stairs`\, a.
Being above stairs; as, an upstairs room.
[1913 Webster]