An adjective meaning liable to catch fire; the subject of strict regulations that vary from country to country especially with regard to furnishings for hotels, business premises and private lettings.
Every fabric has a flame test report that is available from the manufacturers and suppliers. Foam should always be FR–fire retardant–and all upholstery covered with a fire retardant liner before adding the top cover.
As a rule of thumb: natural materials are very much safer than synthetic ones, so avoid foam and especially old foam, and be extra careful when choosing fabrics for children’s rooms, fabrics that will be close to open fires, and if you have a night smoker in the house.