the.com/riverboat
A flat-bottomed gambling palace that turned rivers into highways and decks into casinos.
means A shallow-draft boat built to carry people and cargo along rivers, often paddlewheel-driven and once famous for floating gambling.
from Plain English river plus boat, but the legend is American: the 19th-century Mississippi steamboat, smoke-belching and stacked like a wedding cake.
Flat bottomDrafts inches deep to skim sandbars and shallows
Floating casinosGambling went aboard to dodge land-based laws
Mark TwainHis pen name is riverboat slang for two fathoms deep
PaddlewheelsStern or side wheels pushed against the current