estuary - the wide part of a river where it nears the sea; fresh and salt water mixbody of water, water - the part of the earth's surface covered with water (such as a river or lake or ocean); "they invaded our territorial waters"; "they were sitting by the water's edge" firth - a long narrow estuary (especially in Scotland) Humber - an estuary in central northeastern England formed by the Ouse River and the Trent River Para River, Para - an estuary in northern Brazil into which the Tocantins River flows river - a large natural stream of water (larger than a creek); "the river was navigable for 50 miles" |