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

Pluto, a frigid mountainous world with craters and glaciers, is located among icy bodies in the Kuiper Belt, located at the outskirts of our solar system beyond Neptune's orbit – now the farthest planet from the sun. —Eric Lagatta, USA Today, 30 Apr. 2026

Suspicions of possible ties to drug traffickers have long hung over Rocha Mayo, who was born in Badiraguato, the same mountainous municipality in Sinaloa that is the hometown of El Chapo and other cartel bigwigs. —Kate Linthicum, Los Angeles Times, 30 Apr. 2026

Dimitsana and Arcadian mountain trails The heartland of the Peloponnese is Arcadia, a mountainous province of gorges and hills, many precariously topped by medieval towns. —Helen Brown, TheWeek, 30 Apr. 2026

The race to represent California’s 4th Senate District, a mountainous region on California’s eastern border, is gearing up to be a competitive one. —Kate Wolffe, Sacbee.com, 29 Apr. 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