WordNet (r) 3.0 (2006):

dead end
    n 1: a passage with access only at one end [syn: cul, cul de
         sac, dead end]
    2: a situation in which no progress can be made or no
       advancement is possible; "reached an impasse on the
       negotiations" [syn: deadlock, dead end, impasse,
       stalemate, standstill]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "dead end":
   bar, barrier, blank, blank wall, blind, blind alley, blind gut,
   blind-alley, block, blockade, blockage, bottleneck, box, cecal,
   cecum, choked, choked off, choking, choking off, clog, closed,
   congestion, constipation, constricted, contracted, corner,
   costiveness, cul-de-sac, dead, dead-end street, deadlock, embolism,
   embolus, extremity, gorge, halt, hole, impasse, impediment,
   infarct, infarction, jam, obstacle, obstipation, obstruction,
   pocket, sealing off, shut, squeezed shut, stalemate, stand,
   standstill, stop, stoppage, strangulated, strangulation, unopen,
   unopened, unvented, unventilated