Of utmost importance; of outstanding significance or consequence: a momentous occasion; a momentous decision. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "momentous" in a sentence
"The Australian prime minister also noted what she called the "momentous" upheaval in the Middle East, and pledged her alliance with the United States in condemning Iran's nuclear program, and in a call for an Israeli-Palestinian resolution."
"The Federal Communications Commission is holding what it described as a momentous meeting on the Open Internet beginning at 10:30AM ET Tuesday morning."
"After that San Rafael night, Dylan makes what he describes as the momentous shift from 2 to 3."