Wordnet 3.0
NOUN (2)
1.
a former United States executive agency that was responsible for developing atomic bombs during World War II;
2.
code name for the secret United States project set up in 1942 to develop atomic bombs for use in World War II;
The Collaborative International Dictionary of English v.0.48:
Manhattan Project \Manhattan Project\ prop. n. (U. S. History)
A former US agency that was responsible for developing atomic
bombs during World War II.
[WordNet 1.5]
WordNet (r) 3.0 (2006):
Manhattan Project
n 1: a former United States executive agency that was
responsible for developing atomic bombs during World War II
2: code name for the secret United States project set up in 1942
to develop atomic bombs for use in World War II