Jacket meaning : A piece of clothing worn on the upper body outside a shirt or blouse, often waist length to thigh length. A piece of a person's suit, beside trousers and, sometimes, waistcoat; coat (US) A protective or insulating cover for an object (e.g. a book, hot water tank, bullet.) A police record. In ordnance, a strengthening band surrounding and reinforcing the tube in which the charge is fired. The tough outer skin of a baked potato. To enclose or encase in a jacket or other covering.