torpedo boat, small fast warship built specially for using the torpedo as a means of attack. The first modern torpedo boat was the Lightning, built for the British navy in 1877 by the shipyards of Sir John Isaac Thornycroft. Torpedo boats were adopted by most of the world's major navies, but as they increased in size the destroyer was developed as an effective defense against them. They diminished in importance after the Russo-Japanese War (1904-5) and were used sparingly in World War I, but they were widely employed in World War II. At that time torpedo boats, often referred to as PT boats, were commonly used in attacking enemy coastal shipping and light naval forces under cover of darkness and bad weather. They were usually wooden vessels 75 to 125 ft (22.8-38.1 m) long, powered by gasoline or diesel engines and capable of very high speeds.

flying boat: see seaplane.

boat-billed heron or boatbill, a tropical New World heron, Chochlearius chochlearius. With shorter legs and a squatter appearance than most herons, this bird is remarkable chiefly for its broad bill, which is shaped like an overturned boat. Its coloring is dull brown, gray, and black and is similar in both the male and female. It is a nocturnal, shallow-water feeder, living on a diet of fishes and insects; it roosts and nests in trees. The boat-billed heron inhabits mangrove swamps from Mexico to S Brazil. It is classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Ciconiiformes, family Ardeidae.

boat people, term used to describe the Indochinese refugees who fled Communist rule after the Vietnam War (1975) in small boats and the many ethnic Chinese who left Vietnam similarly after China's invasion of Vietnam in 1979. More than one million people became refugees. Many perished, and others, upon reaching other Southeast Asian countries, discovered they could not remain permanently. The United States, Canada, and other nations accepted most of the refugees in the late 1970s and the 1980s. Although people continued to flee Vietnam into the mid-1990s, nearly all later boat people have been regarded as economic, not political, refugees. In 1996 the United Nations decided to end the financing of the camps holding the remaining 40,000 boat people, and Hong Kong, Thailand, Indonesia, Malaysia, and the Philippines returned most of the remaining refugees to Vietnam. The term boat people has also been used to describe political and economic refugees from other areas, such as Haiti, who fled their homelands by similar means.

boat, small, open nautical vessel propelled by sail, oar, pole, paddle, or motor. The use of the term boat for larger vessels, although common, is somewhat improper, but the line between boats and ships is not easy to draw. A number of special types of boat are generally referred to by their individual names rather than by the generic term, e.g., the canoe, the kayak (Eskimo decked canoe), and the umiak (Eskimo open boat). Simple dugouts, made from hollowed-out logs, have been known since prehistoric times to all peoples dwelling on waterways. The ancient Egyptians used boats made of acacia wood and held together with pegs. Modern wooden boats are built in four ways: with fore-and-aft planks laid with their edges flush (carvel-built); with fore-and-aft planks laid with overlapping edges (clinker-built); with inner and outer layers of planks running diagonally in opposite directions; and with planking consisting of large sheets of plywood. Many boats, however, are now made of molded fiberglass or of aluminum. Primitive boats in many parts of the world are stabilized by an outrigger—a parallel float attached by projecting arms. The varieties of boats in modern use are almost infinite. The Chinese junk, with high poop and overhanging bow, is large enough to be classified as a ship; the junk, together with the sampan (a wide, flat-bottomed skiff, often having a mat-covered cabin with living quarters), is a familiar sight in the rivers and coastal waters of East Asia. The lateen-rigged dhow, in which energetic Arab merchants of the Middle Ages plied their trade along all the shores of S Asia and E Africa, is still in use today. A familiar local craft on the Mediterranean is the flat-bottomed, canoelike, pole-driven gondola of the Venetian canals. A typical Mediterranean vessel of ancient times was the galley, usually propelled by oars. Because the northern seas were stormier, the Viking boats, which the Norsemen were building by the 5th cent. A.D., were more seaworthy; they were believed to be the first clinker-built boats. Deckless or half-decked, with elevated bow and stern, these early boats took the Norsemen to all the coasts of Europe and across the Atlantic. The later rugged whaleboat was developed from the Viking type of construction and came to be used for numerous purposes. The fishing boats of the North and Baltic seas, also built on Viking principles, are roughly similar to whaleboats. Another important fishing boat is the dory, a small, versatile, flat-bottomed craft easily transported on shipboard and used in the entire N Atlantic.

in full polychlorinated biphenyl

Any of a class of highly stable organic compounds prepared by the reaction of chlorine with biphenyl, a two-ring compound. The commercial product, a mix of several PCB isomers, is a colourless, viscous liquid that is almost insoluble in water, does not degrade under high temperatures, and is a good electrical insulator (see dielectric). PCBs became widely used as lubricants, heat-transfer fluids, and fire-resistant dielectric fluids in transformers and capacitors in the 1930s and '40s. In the mid 1970s they were found to cause liver dysfunction in humans and came under suspicion as carcinogens; their manufacture and use were consequently restricted in the U.S. and many other countries, though illegal dumping by manufacturers continued. They persist in the environment and have entered the food chain, causing great harm especially to invertebrates and fish.

Learn more about PCB with a free trial on Britannica.com.

Refugees fleeing by boat. The term originally referred to the thousands of Vietnamese who fled their country by sea following the collapse of the South Vietnamese government in 1975. Crowded into small vessels, they were prey to pirates, and many suffered dehydration, starvation, and death by drowning. The term was later applied to waves of refugees who attempted to reach the U.S. by boat from Cuba and Haiti and also to Afghan and other refugees seeking asylum in Australia.

Learn more about boat people with a free trial on Britannica.com.