IPA: /ˈflætˌboʊt/
KK: /ˈflætˌboʊt/
A type of boat that has a flat bottom and square ends, designed for carrying heavy loads on rivers and other shallow waters.
The flatboat was used to transport goods down the river during the summer months.
Flatboat → The word is formed from "flat" (from Old English *flaet*, meaning level or even) and "boat" (from Old English *bat*, meaning a small vessel for traveling on water). A flatboat is a type of boat that is level and designed for shallow waters.
Think of a 'level' ('flat') vessel ('boat') that is used for traveling on water — that's what a flatboat is.