Downproof and semi-opaque down jacket
Downproof indicates a fabric created to prevent feathers from escaping.
A fabric is water repellent after special treatments to make it resist water: the drops of water do not remain on the fabric, but slip away. Water-repellent fabrics have a certain degree of porosity so they are permeable to air and water vapor. They allow the passage of water when the hydrostatic pressure is high (for example during heavy rain).