Blowhole â A nonstandard term when used for porosity. Cluster Porosity â A localized array of porosity having a random geometric pattern. Pipinq â A form of porosity having a length greater than it's width that lies. approximately perpendicular to the weld face. Also known as wormhole porosity. Elongated Porosity â A form of poroslty having a length greater than its width that lies. approximately parallel to the weld axis.