—adv. 1. up the stairs; to or on an upper floor.
2. Informal.in the mind: to be a little weak upstairs. 3. to or at a higher level of authority: You may have to take the matter upstairs. 4. Mil. Slang.at or to a higher level in the air.
5. kick upstairs, to promote (a person) to a higher position, usually having less authority, in order to be rid of him or her.
—adj. Also,up'stair'.of, pertaining to, or situated on an upper floor: an upstairs window; an upstairs apartment.
—n. 1. (usually used with a sing. v.) an upper story or stories; the part of a building or house that is above the ground floor: The upstairs of this house is entirely rented. 2. a higher command or level of authority: We can't take action till we have approval from upstairs.