noun

• (automotive) The crankcase or oil reservoir of an internal combustion engine.
• (nautical) The pit at the lowest point in a circulating or drainage system (FM 55-501).
• (construction) An intentional depression around a drain or scupper that promotes drainage.
• (Scotland) A sudden or heavy fall of rain; a deluge.
  "then, seating himself thus, he replied to him of the east.—'Sounding sump o' rain Saunders Creeshmeloof—saw ye ever a drap o' rain for eight and forty hours after the bonnie sinking sun that sat sae red and sae lang on the summit of Blackwood hills this blessed afternoon? That starry plow o' thine is […]'"

verb

• (intransitive) 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."