cul-de-sac

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

• noun A dead-end street.
• noun An impasse.
• noun Anatomy A saclike cavity or tube open only at one end.

from The Century Dictionary.

• noun A street or alley which has no outlet at one end; a blind alley; a way or passage that leads nowhere.
• noun Specifically In anatomy and zoology, a diverticulum ending blindly; a cæcum or blind gut; some tubular, saccular, or pouch-like part open only at one end.
• noun An inconclusive argument.
• noun Milit., the situation in which an army finds itself when it is hemmed in and has no exit but by the front.

from the GNU version of the Collaborative International Dictionary of English.

• noun A passage with only one outlet, as a street closed at one end; a blind alley; hence, a trap.
• noun (Mil.) a position in which an army finds itself with no way of exit but to the front.
• noun (Anat.) Any bag-shaped or tubular cavity, vessel, or organ, open only at one end.

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

• noun A blind alley or dead end street.
• noun A circular area at the end of a dead end street to allow cars to turn around, designed so children can play on the street, with little or no through-traffic.
• noun An impasse.
• noun medicine A sack-like cavity or tube open at one end only.

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

• noun a passage with access only at one end
• noun a street with only one way in or out