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 Houthis have been at war with Yemen’s government since 2014, when the rebels swept down from their mountainous heartland and seized much of northern and central Yemen. — Ahmed Al-Haj, Los Angeles Times, 10 Sep. 2026

The goal was to destroy the al-Qaida terrorist network responsible for the attacks and to track down its leader, Osama bin Laden, who was hiding in caves in the country’s mountainous terrain. — Michael Collins, USA Today, 10 Sep. 2026

In mountainous country, look for them in the upper contours, from the ridgeline to about a quarter of the way down the slope. — Jim Zumbo, Outdoor Life, 10 Sep. 2026

Those conditions, as well as heavy rains and mountainous terrain, made access even by air difficult at times. — Simone McCarthy, CNN Money, 6 Sep. 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