boundary
     n 1: the line or plane indicating the limit or extent of
          something [syn: {bound}, {bounds}]
     2: a line determining the limits of an area [syn: {edge}, {bound}]
     3: the greatest possible degree of something; "what he did was
        beyond the bounds of acceptable behavior"; "to the limit
        of his ability" [syn: {limit}, {bounds}]
Source: WordNet® 2.0