broadly, a railing that connects the tops of a row of vertical balusters (shaped rails), found at the edges of balconies, terraces, or bridges, often as an ornamental element;
e.g. The balcony had a carved stone balustrade around it.
(noun)
broadly, a low barrier or wall that serves as a protective edge on a balcony, roof, or bridge but that also has an ornamental purpose;
e.g. He was leaning on the balustrade and watching us.