Leo. 1898–1964, US physicist, born in Hungary, who originated the idea of a self-sustaining nuclear chain reaction (1934). He worked on the atomic bomb during World War II but later pressed for the international control of nuclear weapons
(zĭl'ərd) Hungarian-born American physicist who introduced the concept of the nuclear chain reaction. With Enrico Fermi, he built the world's first nuclear reactor. Szilard was instrumental in the development of the atomic bomb.