Manhattan Project

American  

noun

1. 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.

---

Manhattan Project British  

noun

1. (during World War II) the code name for the secret US project set up in 1942 to develop an atomic bomb

---

Manhattan Project Cultural  

1. The code name for the effort to develop atomic bombs (see also atomic bomb) for the United States during World War II. The first controlled nuclear reaction took place in Chicago in 1942, and by 1945, bombs had been manufactured that used this chain reaction to produce great explosive force. The project was carried out in enormous secrecy. After a test explosion in July 1945, the United States dropped atomic bombs on the Japanese cities of Hiroshima (see also Hiroshima) and Nagasaki.

---

Etymology

Origin of Manhattan Project

Extracted from U.S. Army Corps of Engineers Manhattan District and DSM (Development of Substitute Materials) Project

Example Sentences

He compares the initiative to the Manhattan Project.

From Barron's • May 7, 2026

He compares the initiative to the Manhattan Project.

From Barron's • May 7, 2026

Many members believe they’ve lost loved ones to radiation, or were themselves likely impacted by early-life exposure as children of Manhattan Project engineers.

From Los Angeles Times • Mar. 27, 2026

Hassabis had envisioned a Manhattan Project for intelligence, hiring the brightest minds in his field and inventing an agent that played multiple Atari videogames.

From The Wall Street Journal • Mar. 25, 2026

Oppenheimer couldn’t work on the Manhattan Project until he got security clearance from the army.

From "Bomb" by Steve Sheinkin