WordWeb Online

1. The line or plane indicating the limit or extent of something
   - bound, bounds
    
2. A line determining the limits of an area
   - edge, bound
    
3. The greatest possible degree of something
   "to the boundary of his ability";
   - limit, bound

Derived forms: boundaries

Type of: extent, extremity, line

Encyclopedia: Boundary, British Columbia Boundary Boundary, Derbyshire Boundary, Staffordshire Boundary, Leicestershire