A long-bodied chiefly marine fish with a cartilaginous skeleton, a prominent dorsal fin, and toothlike scales. Most sharks are predatory, although the largest kinds feed on plankton. A small Southeast Asian freshwater fish with a sharklike tail, popular in aquariums. A light grayish-brown European moth, the male of which has pale silvery hind wings. A person who unscrupulously exploits or swindles others. An expert in a specified field.