1. A roughly circular or elongated unbonded area between plies of laminated constructions, as in wood veneer. Usually caused by entrapped moisture. Also called steam blow.
2.A spongy raised portion of a roofing membrane, where separation of the felts has occurred or the membrane is not bonded to the substrate as a result of the expansion of water and air trapped in the membrane.
3. A raised spot on the surface of the metal caused by expansion of gas in a subsurface zone during thermal treatment.
4.A raised area on the surface of a molded plastic caused by the pressure of internal gases on its incompletely hardened surface.
5. See blistering.
6. A convex, raised area on the surface of a pipe which indicates an internal separation.