A part that forms the outer edge of something. A decorative strip around the edge of something, such as fabric. A strip of ground, as at the edge of a garden or walk, in which ornamental plants or shrubs are planted. The line or frontier area separating political divisions or geographic regions; a boundary. To put a border on. To lie along or adjacent to the border of: Canada borders the United States. To lie adjacent to another: The United States borders on Canada. To be almost like another in character: an act that borders on heroism.