Basement floor area (4)
I believe the answer is:
sump
(Other definitions for sump that I've seen before include "Lubrication reservoir" , "oil well?" , "Into which liquids drain" , "Cesspool" , "Oil store" .)
I believe the answer is:
sump
(Other definitions for sump that I've seen before include "Lubrication reservoir" , "oil well?" , "Into which liquids drain" , "Cesspool" , "Oil store" .)