outlet (out'-let). (a) The relatively narrow opening at the lower end of a lake through which water is discharged into an outflowing stream or other body of water. Syn: outflow. (b) A stream flowing out of a lake, pond, or other body of standing water; also, the channel through which such a stream flows. (c) The lower end of a watercourse where its water flows into a lake or sea; e.g. a channel, in or near a delta, diverging from the main river and delivering water into the sea. (d) A crevasse in a levee.