Noun

1. A hollow or pit into which liquid drains, such as a cesspool, cesspit or sink.
2. The lowest part of a mine shaft into which water drains.
3. A completely flooded cave passage, sometimes passable by diving.
4. The crankcase or oil reservoir of an internal combustion engine.
5. The pit at the lowest point in a circulating or drainage system. (FM 55-501)
6. An intentional depression around a drain or scupper that promotes drainage.

Verb

1. Of a cave passage, to end in a sump, or to fill completely with water on occasion.
   • We discovered a new passage, but it sumped after 100 metres.
   • This low passage sumps quickly after moderate rainfall.

Noun

1. swamp (type of wetland)