boat A boat is a watercraft of any size which is able to float or plane on water. Difficult to distinguish from "ships". Similar to mountains and hills. " In naval terms, a boat is a vessel small enough to be carried aboard another vessel (a ship). Another less restrictive definition is a vessel that can be lifted out of the water. Some definitions do not make a distinction in size, as bulk freighters 1,000 feet (300 m) long on the Great Lakes are called oreboats. For reasons of naval tradition, submarines are usually referred to as 'boats' rather than 'ships', regardless of their size and shape." - Wikipedia:Boat watercraft