sump

an internal collector of water from a gutter system for discharge to a connecting downpipe

a pit formed in the floor of a structure or sunk below the general base of an excavation, to collect unwanted water for the purpose of facilitating its removal

a collector of rainwater, generally of rectangular shape, in the sole of a box gutter and connected to a downpipe within the building perimeter, which is used to increase the head of water at the entry to the downpipe and thus increase the capacity of the downpipe

<stormwater> subsurface water collection point or pit connected to a stormwater system, and usually covered by a cast iron grate
See also: drainage pit

recess or small chamber into which a liquid is drained to facilitate its removal