noun

• A covered pouch, usually one of a pair, laid across the back of a horse, donkey, or mule behind its saddle, or hanging over the rear wheel of a motorcycle; often made of leather or (on a motorcycle) a rigid material.
• (cycling, nonstandard, by extension) pannier
• (cycling) A seat pack or a seat bag (a pouch or a small bag attached to the seat or seat post of a bicycle)
• (in the plural, US, informal) Loose fatty flesh on a person's upper thighs or buttocks, that hangs like saddlebags.
• (architecture) A style of house with two rooms separated by a small hall and open space.