1. down the stairs.
2. to or on a lower floor.
Also,down'stair".pertaining to or situated on a lower floor, esp. the ground floor.
1. (used with a sing. v.) the lower floor or floors of a building: The downstairs is being painted.
2. the stairway designated for use by people descending: Don't try to go up the downstairs.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.