boundary

Universal Words noun (plural boundaries) 1 a real or imagined line that marks the limits or edges of sth and separates it from other things or places; a dividing line: national boundaries * (BrE) county boundaries * boundary changes / disputes * The fence marks the boundary between my property and hers. * Scientists continue to push back the boundaries of human knowledge. * the boundary between acceptable and unacceptable behaviour * He could just see her beyond the boundary wall of the cemetery. * to extend the boundaries of high art to include some popular music 2 (in cricket) a hit of the ball that crosses the boundary of the playing area and scores extra points: He hit 13 boundaries from 183 balls.