2. The quantity contained in a basin.
5. (Science: physics) a circular or oval valley, or depression of the surface of the ground, the lowest part of which is generally occupied by a lake, or traversed by a river. The entire tract of country drained by a river, or sloping towards a sea or lake.
6. (Science: geology) An isolated or circumscribed formation, particularly where the strata dip inward, on all sides, toward a center; especially applied to the coal formations, called coal basins or coal fields.