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

The film’s focus is well-balanced between celebrating the history of the studio and of this legendary artist, who recorded all 39 of the songs featured in this box set at Electric Lady in the final days of his short but momentous life. —George Varga, The Mercury News, 16 Dec. 2024

So, with the AI revolution well underway, here’s my overview of the year’s AI highlights – including the game-changing breakthroughs and discoveries setting the stage for an even more momentous 2025. —Bernard Marr, Forbes, 16 Dec. 2024

The big story Just over twelve months ago, thousands of Indians gathered at Delhi’s Red Fort as Prime Minister Narendra Modi delivered his speech on the momentous occasion of India’s 75th Republic Day. —Amala Balakrishner, CNBC, 12 Dec. 2024

The parting of ways caps off a year of momentous and often unexpected designer comings and goings at the likes of Chanel, Celine, Dries Van Noten, Fendi, Alberta Ferretti, Missoni, Helmut Lang and others. —Miles Socha, WWD, 11 Dec. 2024

Word History

First Known Use

1631, in the meaning defined above

Kids Definition

momentous

adjective

mo·​men·​tous mō-ˈment-əs 

: very important

a momentous decision

momentously adverb