Entry 1 sense Webster, 1913 downstairs /doun'-stĕrz'/ · down·stairs · IPA /daʊnˈstɛɹz/ 01 adv. Down the stairs; to a lower floor; as, she headed downstairs as soon as she heard the horn. 1. Down the stairs; to a lower floor; as, she headed downstairs as soon as she heard the horn.