n. 1. Water flowing in from behind.n. Water thrown back by the turning of a water-wheel or the paddles of steamboats, etc.n. Water held or forced back, as in a mill-race or in a tributary stream, in consequence of some obstruction, as a dam or flood.n. An artificial accumulation of water obtained at high tide and reserved in reservoirs, to be discharged at low tide for clearing off deposits in channel-beds and tideways.n. A creek or arm of the sea which runs parallel to the coast, having only a narrow slip of land between it and the sea, and communicating with the latter by barred entrances.