1. of great importance or significance, especially in having a major effect on future events

Examples

• The signing of the peace treaty was a momentous occasion.
• She made the momentous decision to change careers.
• The discovery of DNA’s structure was momentous for science.
• Their wedding day was the most momentous event of their lives.
• The court’s ruling had momentous implications for civil rights.
• He paused before making such a momentous announcement.