fire escape

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A structure or device, such as an outside stairway attached to a building, erected for emergency exit in the event of fire.

from The Century Dictionary.

• noun Any apparatus or structure designed to enable persons to escape from the upper windows of a building in case of fire.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun any of the series of emergency doors, ladders, or stairs used to evacuate a building if a fire breaks out.
• noun the entire escape route viewed as a whole.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a stairway (often on the outside of a building) that permits exit in the case of fire or other emergency