nuclear

adjective

nu·​cle·​ar ˈnü-klē-ər  ˈnyü- 

 nonstandard  -kyə-lər

1

: of, relating to, or constituting a nucleus

annexation of the suburban fringe by the nuclear metropolis

—W. H. Wickwar

2

a

: of or relating to the atomic nucleus

nuclear reaction

nuclear physics

b

: used in or produced by a nuclear reaction (such as fission)

nuclear fuel

nuclear waste

nuclear energy

c(1)

: being a weapon whose destructive power derives from an uncontrolled nuclear reaction

(2)

: of, produced by, or involving nuclear weapons

the nuclear age

nuclear war

(3)

: armed with nuclear weapons

nuclear powers

d

: of, relating to, or powered by nuclear energy

a nuclear submarine

the nuclear debate

a nuclear plant

How do you pronounce nuclear?: Usage Guide

Though disapproved of by many, pronunciations ending in \-kyə-lər\ have been found in widespread use among educated speakers including scientists, lawyers, professors, congressmen, U.S. cabinet members, and at least two U.S. presidents and one vice president. While most common in the U.S., these pronunciations have also been heard from British and Canadian speakers.

Phrases

go nuclear

informal

: to become wildly excited or upset : go berserk

To say the crowd went wild is an understatement. The crowd went nuclear. Outside the stadium, cars were overturned and fires were set. We sportswriters huddled inside, fearing for our lives.

—Tony Kornheiser

Examples of nuclear in a Sentence

Recent Examples on the Web

The fighting came after Iranian officials had engaged in diplomatic meetings in Geneva, New York and Istanbul on Friday, which failed to produce any breakthroughs, even as President Trump considers whether to join Israel in launching an attack on Iran's nuclear facilities. —Kate Bartlett, NPR, 21 June 2025

But the attempt to take out Iran’s Fordow nuclear facility promises to be protracted. —Paul Bedard, The Washington Examiner, 21 June 2025

Key Background Tensions between Iran and Israel first erupted on Friday, when the Israel military carried out unilateral strikes against key nuclear facilities and killed several top Iranian generals and nuclear scientists. —Siladitya Ray, Forbes.com, 21 June 2025

Yet Trump, whose administration had entered into talks with Iran aimed at reaching an agreement on the country's nuclear program, has backed the Israeli offensive and has openly contemplated joining the Israeli campaign through strikes on Iranian nuclear facilities. —Tom O'Connor, MSNBC Newsweek, 21 June 2025

Word History

Etymology

nucle(us) + -ar

First Known Use

1822, in the meaning defined at sense 1

Phrases Containing nuclear

• nuclear capability
• nuclear energy
• nuclear family
• nuclear fission
• nuclear-free
• nuclear fusion
• nuclear magnetic resonance
• nuclear medicine
• nuclear membrane
• nuclear option
• nuclear power
• nuclear reaction
• nuclear reactor
• nuclear sap
• nuclear winter
• post-nuclear

Rhymes for nuclear

• antinuclear
• internuclear
• intranuclear
• mononuclear
• perinuclear
• polynuclear
• supranuclear
• thermonuclear
• binuclear
• polymorphonuclear

Video

'Mispronunciations' That May Be Fine

'Mischievous,' 'nuclear,' and other words to pronounce with caution.

Kids Definition

nuclear

adjective

nu·​cle·​ar ˈn(y)ü-klē-ər 

1

: of, relating to, or being a nucleus (as of a cell)

2

: of, relating to, or using the atomic nucleus

nuclear reactions

3

: being or relating to energy or a weapon that involves a nuclear reaction

nuclear energy

a nuclear war

nuclear power plants

Medical Definition

nuclear

adjective

nu·​cle·​ar ˈn(y)ü-klē-ər 

1

: of, relating to, or constituting a nucleus

2

: of, relating to, or utilizing the atomic nucleus, atomic energy, the atomic bomb, or atomic power