mountainous

adjective

moun·​tain·​ous ˈmau̇n-tə-nəs 

ˈmau̇nt-nəs

1

: containing many mountains

2

: resembling a mountain : huge

mountainously adverb

mountainousness noun

Synonyms

• vast
• huge
• gigantic
• enormous
• giant
• massive
• tremendous
• colossal
• mammoth
• immense
• astronomical
• monumental
• astronomic
• monstrous

Examples of mountainous in a Sentence

the seemingly mountainous obstacles he had to overcome while growing up

Recent Examples on the Web

This mountainous region of the Hudson Valley is no more than three hours from Manhattan with quite the idyllic reputation, and for good reason. —Elly Leavitt, Vogue, 1 Oct. 2025

The Huajiang Grand Canyon Bridge opened to traffic for the first time on Sunday — and now claims to be the world’s tallest and largest span bridge in a mountainous area, according to Chinese state media. —Ashley J. Dimella, FOXNews.com, 30 Sep. 2025

Riding from Charlotte and traversing through the mountainous terrain of the western part of North Carolina, the gravity of it all wasn’t lost on Grant Williams. —Roderick Boone, Charlotte Observer, 26 Sep. 2025

Colorado’s wolves returned to areas near the Utah border this month, though most wolf activity remained confined to the state’s more mountainous terrain. —Elise Schmelzer, Denver Post, 24 Sep. 2025

Word History

Etymology

Middle English mounteynous, borrowed from Anglo-French muntaignus, from muntaigne, mountaigne mountain + -us -ous

First Known Use

14th century, in the meaning defined at sense 1

Kids Definition

mountainous

adjective

moun·​tain·​ous ˈmau̇nt-ᵊn-əs 

-nəs

1

: having many mountains

2

: resembling a mountain : huge