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

To access a plethora of mountainous backcountry trails, go east. —Lydia Mansel, Travel + Leisure, 3 Dec. 2025

Eleven days earlier, Union High School football coach Travis Turner is believed by his family to have walked out of his home in Appalachia carrying a firearm, disappearing into the thick, mountainous woods. —Alisha Ebrahimji, CNN Money, 1 Dec. 2025

Seasonal rains frequently cause flooding and landslides in Indonesia, an archipelago of 17,000 islands where millions of people live in mountainous areas or near fertile flood plains. —Arkansas Online, 30 Nov. 2025

The area is beautiful and mountainous and offers mighty fine deer and elk hunting. —William J. McRae, Outdoor Life, 26 Nov. 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