A topographic region in which all water drains to a common outlet.
The lowest part of a mineshaft into which water drains.
The crankcase or oil reservoir of an internal combustion engine.
A hollow or pit into which liquid drains, such as a cesspool, cesspit or sink.
A completely flooded cave passage, sometimes passable by diving.
The pit at the lowest point in a circulating or drainage system (FM 55-501).
An intentional depression around a drain or scupper that promotes drainage.
Of a cave passage, to end in a sump, or to fill completely with water on occasion.