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

see also:

go nuclear

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.

Examples of nuclear in a Sentence

Recent Examples on the Web

Enabling next-generation geothermal and nuclear projects is great too. — Jordan Blum, Fortune, 11 Oct. 2026

Terrestrial Energy wants federal regulators to formally confirm that assembling this turbine wing falls outside federal nuclear construction rules. — Aman Tripathi, Interesting Engineering, 10 Oct. 2026

Then Sean moves away and grows up to become a spy who, after wrapping up a mission involving smuggling a nuclear warhead for reasons unknown, decides to pay an impromptu visit to his tweenage buddies. — Alison Willmore, Vulture, 9 Oct. 2026

Sharon Packer, a longtime nuclear engineer with Utah Shelter Systems, said her current slate includes an expansive, multimillion-dollar bunker for 400 employees and family members of a private company. — Megan Buerger, Washington Post, 9 Oct. 2026

Word History

Etymology

nucle(us) + -ar

First Known Use

1822, in the meaning defined at sense 1

Phrases Containing nuclear

• go 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