mountainous

adjective

moun·​tain·​ous ˈmau̇n-tə-nəs 

ˈmau̇nt-nəs

1

: containing many mountains

mountainous wilderness

2

: resembling a mountain : huge

a stormy ocean with mountainous waves

mountainously adverb

mountainousness noun

Synonyms of mountainous

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

Examples of mountainous in a Sentence

the seemingly mountainous obstacles he had to overcome while growing up

Recent Examples on the Web

The mansions are in the Bio Barray neighborhood, part of which has been built illegally in the mountainous Western Area Peninsula National Park, which Sierra Leone's government has proposed as a UNESCO World Heritage Site. —Ed Davey The Associated Press, Arkansas Online, 19 Feb. 2026

In the cooler fall and winter months, natural food sources decline, and snow covers mountainous regions like Tahoe. —Madison Dapcevich, Outside, 19 Feb. 2026

The expedition required traversing up to four miles of mountainous terrain while carrying food and supplies and staying overnight in remote huts. —Stephen Sorace, FOXNews.com, 18 Feb. 2026

My father was born in mountainous Naranjito, Puerto Rico. —Letters To The Editor, The Orlando Sentinel, 18 Feb. 2026

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