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

Iran insists its nuclear activities are for civilian energy purposes only. —Kim Hjelmgaard, USA Today, 17 May 2025

In the film, paternalistic aliens cut electricity worldwide to force humanity to reconsider its nuclear arms race. —Marianne Lehnis, Forbes.com, 16 May 2025

Win McNamee - Getty Images In an interview with NBC on Wednesday, Ali Shamkhani—a key political, military and nuclear adviser to the Iranian Supreme Leader Ayatollah Ali Khamenei—said that the country is ready to sign a nuclear deal with the U.S., subject to conditions. —Callum Sutherland, Time, 16 May 2025

Arms control advocate Yet Garwin was also a longtime advocate of nuclear arms control and ultimately of nuclear disarmament. —Matthew Bunn, The Conversation, 16 May 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