atom bomb

US: (at′əm bom′)

WordReference Random House Unabridged Dictionary of American English © 2026

at′om bomb′. 

1. See atomic bomb. 

• 1940–45

at•om-bomb  (at′əm bom′), v.t. 

1. to bomb (a target) with an atomic bomb.

v.i. 

2. to atom-bomb a target.

• 1940–45

WordReference Random House Learner's Dictionary of American English © 2026

aˈtom•ic ˈbomb or ˈat•om ˈbomb,n. [countable]

1. Physics a bomb whose power comes from splitting atoms of certain elements.

Also called A-bomb.

WordReference Random House Unabridged Dictionary of American English © 2026

atom′ic bomb′, 

1. a bomb whose potency is derived from nuclear fission of atoms of fissionable material with the consequent conversion of part of their mass into energy.
2. a bomb whose explosive force comes from a chain reaction based on nuclear fission in U-235 or plutonium.
Also, atom bomb. Also called A-bomb, fission bomb. 
• 1910–15

Collins Concise English Dictionary © HarperCollins Publishers::

atomic bomb, atom bomb noun

1. a type of bomb in which the energy is provided by nuclear fission. Uranium-235 and plutonium-239 are the isotopes most commonly used in atomic bombs
   Also called: A-bomb, fission bomb
   Compare fusion bomb