Definition: A deformable material which prevents the passage of matter through the joint formed when two faces are joined. it may be metallic or nonmetallic, lubricated or impregnated, solid or hollow cross section. it may be made to any predetermined dimension and shape. excludes flat disks, items made of felt material and items having joints. for round metal and plastic items with an aperture and a solid rectangular cross section, see washer, flat; shim; bearing, washer, thrust; and spacer ring. excludes disk, valve; seal, nonmetallic angle; seal, nonmetallic channel; seal, nonmetallic special shaped section; shielding gasket, electronic; and ring, sealing jar.