IPA: /ˈsɛspuːl/
KK: /ˈsɛspul/
A deep hole or pit that collects waste, especially sewage, and can also refer to a very dirty or morally corrupt place.
The abandoned building had turned into a cesspool of garbage and neglect.
Cesspool is formed from "cess" (from Old French *cesser*, meaning to cease or stop) and "pool" (from Old English *pōl*, meaning a small body of water). The word refers to a pit or reservoir where waste is collected and stopped, resembling a stagnant pool of refuse.
Think of a place where waste 'ceases' to flow ('cess') and collects in a 'pool' — that's what a cesspool is.
No commonly confused words.