exōstra, ae, f., = ἐξώστρα.
I A machine in the theatre , by which the back part of the stage was turned towards the spectators; transf. of any thing public : quibuscum jam in exostra helluatur, Cic. Prov. Cons. 6, 14.—
II A hanging bridge , applied by besiegers to the walls of a besieged city , Veg. Mil. 4, 21.