What does "brink" mean?

Brink: The edge, margin, or border of a steep place, as of a precipice; a bank or edge, as of a river or pit; a verge; a border; as, the brink of a chasm. Also Fig. "The brink of vice." Bp. Porteus. "The brink of ruin." Burke. The plashy brink of weedy lake. Bryant.