<p><strong>Adverb</strong></p><ul><li>up the stairs; to or on an upper floor.</li><li>Informal: in the mind: to be a little weak upstairs.</li><li>to or at a higher level of authority: You may have to take the matter upstairs.</li><li>Military Slang: at or to a higher level in the air.</li></ul><p><strong>Adjective</strong></p><ul><li>Also upstairs.</li><li>of, relating to, or situated on an upper floor: an upstairs window; an upstairs apartment.</li></ul><p><strong>Noun</strong></p><ul><li>plural upstairs (usually used with a singular verb): 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.</li><li>a higher command or level of authority: We can't take action till we have approval from upstairs.</li></ul>