(a) A well, fountain, spring. (b) A deep, still, smooth part of a river.

Something which is steady. spec. in Newfoundland, a part of a river which has little or no perceptible current.

A stretch or reach of comparatively still water in a river.

attributive, as slack-water basin, slack-water deposit, slack-water period, slack-water stream.

A part of a river lying outside of the current, or one in which the flow is lessened by a lock or dam. Also figurative.