momentous

adjective

mo·​men·​tous mō-ˈmen-təs 

mə-

: having great or lasting importance : consequential, significant

a momentous decision

a momentous event/occasion

The Senate begins a momentous debate on health care today …

—The New York Times

Deydey usually talked about his travels, the places he'd seen and the people, the close calls and momentous encounters with animals, weather, other Anishinabeg, and best of all, ghosts.

—Louise Erdrich

The late nineteenth century was strewn with inventions. Many were momentous, but few affected men and women more closely than the bicycle and its motorized offspring: motorcycle, motor-car and aeroplane.

—Eugen Weber

momentously adverb

a momentously important decision

… a … twist that is executed differently from the comic book story, but is just as dramatically and momentously presented.

—The Philippines Daily Inquirer

momentousness noun

But other East Europeans had little time to marvel at the momentousness of the moment. Just one day after the fall of the [Berlin] Wall, Bulgaria's dour leader of 35 years, Todor Zhivkov, was ousted.

—Stephen E. Deane

Synonyms of momentous

• major
• important
• significant
• historic
• big

Examples of momentous in a Sentence

My college graduation was a momentous day in my life.

a momentous occasion that will go down in the history books

Recent Examples on the Web

White House officials said the orders would prevent a large number of children from receiving birthright citizenship, hailing it as momentous. — Kevin Rector, Los Angeles Times, 7 Aug. 2026

So Flight 14 could be momentous, provided SpaceX gets permission from regulators to make an attempt. — Mike Wall, Space.com, 4 Aug. 2026

And this being France’s national flag carrier, meal time is its own momentous event. — Jessica Puckett, Condé Nast Traveler, 1 Aug. 2026

And such momentous changes as bringing back Eric Bieniemy as offensive coordinator and the Chiefs signing Super Bowl MVP Kenneth Walker III to revive their running game heralded Reid’s recognition of the moment. — Vahe Gregorian july 31, Kansas City Star, 31 July 2026

Word History

First Known Use

1631, in the meaning defined above

Rhymes for momentous

• apprentice
• placentas
• portentous
• filamentous
• ligamentous
• mentis
• prentice

Kids Definition

momentous

adjective

mo·​men·​tous mō-ˈment-əs 

: very important

a momentous decision

momentously adverb