short for atomic bomb, a bomb that uses the energy from the splitting of atoms to cause an explosion of tremendous force, accompanied by a blinding light. The first atomic bomb was successfully tested by the United States in July 1945. In the final stages of World War II the United States dropped atomic bombs first on Hiroshima and then three days later on Nagasaki to force the Japanese to surrender. See also Hiroshima and war, last in this glossary.—State of ManCongress Approved Gls (14.5.92)