A directive to string musicians to perform the indicated passage with the bow at (over or near) the bridge of the instrument rather than in the usual position, which is between the fingerboard and the bridge.
See also [Eng.] at the bridge; [Fr.] sur le chevalet; [Fr.] près du chevalet; [Fr.] contre le chevalet; [Ger.] am Steg; [It.] sul ponticello.
Video example: Sharon Polifrone, Assistant Concertmaster, Lyric Opera Orchestra, Chicago, Illinois