The meaning of this word depends very much on circumstances and context. If there is no other clue, it probably means a motor cruiser – a motor boat with habitable accommodation. If the context is one of sailing craft then it means a boat whose design was not constrained by any arbitrary rating formulae devised for the amusement of racing yachtsmen. If compounded in the form Cruiser-racer it implies that the boat was designed to fit the rating formula but that the builder hopes he can sell her to cruising people in spite of that.