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Synonyms

momentous

American  
[moh-men-tuhs] / moʊˈmɛn təs /

adjective

  1. of great or far-reaching importance or consequence.

    a momentous day.

    Synonyms:
    serious, crucial, critical, vital
    Antonyms:
    trifling, trivial

momentous British  
/ məʊˈmɛntəs /

adjective

  1. of great significance

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Synonym Usage

See heavy.

Other Word Forms

Etymology

Origin of momentous

First recorded in 1645–55; moment + -ous

Explanation

Momentous describes an important event or moment in time. It is used for a time of great consequence or for a major accomplishment, and is almost always reserved for good things. When a moment is so great you know you'll never forget it, you have just experienced something momentous. It can be personal — perhaps the day you were named prom queen; or something historic — like the day Elizabeth was named Queen of England. Momentous and momentary share the root word moment but momentary describes just one fleeting moment in time. A momentary occurrence can certainly be momentous, but it's not always the case.

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Vocabulary lists containing momentous

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

As she approached the momentous milestone, Saar appeared more interested in creating new art than in dissecting her legacy.

From Los Angeles Times Jul. 27, 2026

This raises a momentous question: If diagnosed with a terminal illness, how can you weigh the decision in a calm, unhurried, fully informed manner?

From MarketWatch Jul. 20, 2026

Associated Newspapers executive Paul Dacre said today was a "momentous victory"

From BBC Jul. 7, 2026

Meanwhile, the development of autonomous systems guided by artificial intelligence heralds an even more momentous turn.

From The Wall Street Journal Jul. 7, 2026

On Christmas Eve 1906, from a wind-lashed transmitting station overlooking the Atlantic Ocean at Brant Rock, Massachusetts, a momentous sound was heard.

From "The Story of Music" by Howard Goodall

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