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

For nearly four decades, Armenia and Azerbaijan have skirmished with each other, primarily over Nagorno-Karabakh, a mountainous region that both countries claim. —Mark Temnycky, Forbes.com, 10 Sep. 2025

In a small region of the mountainous forests in Brazil, the peaks meet the clouds and humidity fills the air. —Irene Wright, Miami Herald, 9 Sep. 2025

Cedar, a wood that’s native to the Himalayas but grows in mountainous regions across the globe from North Africa to Virginia, produces an oil that noses commonly use in men’s fragrances. —Justin Fenner, Robb Report, 9 Sep. 2025

The area is a vast, rural, mountainous tract of forests with a political ethos that resembles Texas more than Los Angeles, San Francisco, the state capital of Sacramento, and other liberal Democratic environs. —David Mark, The Washington Examiner, 5 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