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

PaleyFest 2025 is shaping up to be a celebratory occasion, with panels slated for several momentous premieres and finales. —Claire Franken, TVLine, 27 Jan. 2025

For Justin Marks, the partnership represents a momentous occasion. —Joel Thayer, Newsweek, 27 Jan. 2025

Naturally, several aspects of this momentous executive order will be fiercely litigated. —The Editors, National Review, 23 Jan. 2025

What’s a good way for a ragtag group of video-game heroes (or for a heroic rogue flying solo) to either get some respite from the action or gear up for a momentous narrative? —Angelica Frey, JSTOR Daily, 21 Jan. 2025

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