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