WordNet (r) 3.0 (2006):

roadblock
    n 1: any condition that makes it difficult to make progress or
         to achieve an objective; "intolerance is a barrier to
         understanding" [syn: barrier, roadblock]
    2: a barrier set up by police to stop traffic on a street or
       road in order to catch a fugitive or inspect traffic etc.
       [syn: roadblock, barricade]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "roadblock":
   arch dam, backstop, bamboo curtain, bank, bar, barrage, barricade,
   barrier, bear-trap dam, beaver dam, blank wall, block, blockade,
   boom, breakwater, breastwork, brick wall, buffer, bulkhead,
   bulwark, cofferdam, dam, defense, dike, ditch, earthwork,
   embankment, fence, gate, gravity dam, groin, hydraulic-fill dam,
   iron curtain, jam, jetty, leaping weir, levee, logjam, milldam,
   moat, mole, mound, parapet, portcullis, rampart, rock-fill dam,
   seawall, shutter dam, stone wall, stop, wall, weir, wicket dam,
   work