This term is loosely applied to any Fishing Vessel with integral motor propulsion, whether intended for use as a Drifter, as a Trawler or in line-fishing. Such vessels vary considerably in size, form and construction.
The term is also applied more specifically to a type of vessel (known colloquially as an 'MFV') built for naval service as light support craft, fleet tenders, diving vessels and patrol duties, but suitable for sale and civilian use when no longer required.