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

• big
• consequential
• earth-shattering
• earthshaking
• eventful
• historic
• important
• major
• material
• meaningful
• monumental
• much
• significant
• substantial
• tectonic
• weighty

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

Saturday Night Live is coming to the end of a rather momentous season, one which included its 50th anniversary that was as star-studded as anyone could have expected. —Peter White, Deadline, 7 May 2025

The Mavs will have a momentous offseason after trading franchise star Luka Doncic to the Los Angeles Lakers for a package centered around star center Anthony Davis, and the draft will be one of their best chances to add talent. —Lawrence Dow, Fort Worth Star-Telegram, 6 May 2025

Comments On the last day of filming his final Conjuring movie, Patrick Wilson didn't have some momentous cathartic moment. —EW.com, 6 May 2025

Disney’s chief executive Bob Iger built his reputation on doing some of the most momentous deals in the media industry. —Caroline Reid, Forbes.com, 5 May 2025

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