a spiral passage for directing the water from a penstock around a water turbine and into the rotor.
- Spiral crest
spiral crest n. The thickened periosteal lining of the bony cochlea forming the outer wall of the cochlear duct to which the basal lamina attaches. Also called spiral ligament of cochlea.
- Spiral fold of cystic duct
spiral fold of cystic duct n. A series of crescent-shaped folds of mucous membrane in the upper part of the cystic duct, arranged in a somewhat spiral manner. Also called spiral valve.
- Spiral fracture
spiral fracture n. A fracture in which the bone has been twisted apart and the line of break is helical.
noun, Astronomy. 1. a galaxy having a spiral structure. spiral galaxy noun 1. a galaxy consisting of an ellipsoidal nucleus of old stars from opposite sides of which arms, containing younger stars, spiral outwards around the nucleus. In a barred spiral the arms originate at the ends of a bar-shaped nucleus spiral galaxy (spī’rəl) A […]