Giant Gi"ant, a. Like a giant; extraordinary in size, strength, or power; as, giant brothers; a giant son. Giant cell. (Anat.) See Myeloplax. Giant clam (Zo["o]l.), a bivalve shell of the genus Tridacna, esp. T. gigas, which sometimes weighs 500 pounds. The shells are sometimes used in churches to contain holy water. Giant heron (Zo["o]l.), a very large African heron (Ardeomega goliath). It is the largest heron known. Giant kettle, a pothole of very large dimensions, as found in Norway in connection with glaciers. See Pothole. Giant powder. See Nitroglycerin. Giant puffball (Bot.), a fungus (Lycoperdon giganteum), edible when young, and when dried used for stanching wounds. Giant salamander (Zo["o]l.), a very large aquatic salamander (Megalobatrachus maximus), found in Japan. It is the largest of living Amphibia, becoming a yard long. Giant squid (Zo["o]l.), one of several species of very large squids, belonging to Architeuthis and allied genera. Some are over forty feet long.