The Oxford Thesaurus An A-Z Dictionary of Synonyms - barrier n.

1) bar, fence, railing, wall; ditch, ha-ha: A barrier was erected at each end of the street. This barrier will keep the dingoes from killing the sheep. 2) obstacle, bar, obstruction, block, impediment, hindrance: Neither race, nor creed, nor colour shall be a barrier to success. 3) boundary, boundary-line, limit, frontier: No mountain barrier lay between France and Flanders.