(during World War II) the code name for the secret US project set up in 1942 to develop an atomic bomb
Also called: Manhattan District
Manhattan Project in American English
noun
U.S. History
the unofficial designation for the U.S. War Department's secret program, organized in 1942, to explore the isolation of radioactive isotopes and the production of an atomic bomb: initial research was conducted at Columbia University in Manhattan
Word origin
[extracted from U.S. Army Corps of Engineers Manhattan District and DSM (Development of Substitute Materials) Project]