Definition of "sump"

A hollow or pit into which liquid drains, such as a cesspool, cesspit or sink.  examples

The lowest part of a mineshaft into which water drains.  examples

A completely flooded cave passage, sometimes passable by diving.  examples

(automotive) The crankcase or oil reservoir of an internal combustion engine.  examples

(nautical) The pit at the lowest point in a circulating or drainage system (FM 55-501).  examples

(construction) An intentional depression around a drain or scupper that promotes drainage.  examples

(intransitive) Of a cave passage, to end in a sump, or to fill completely with water on occasion.  examples