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

Dry and hot conditions, with temperatures climbing above 100 degrees, in mountainous terrain make containing the blaze difficult for thousands of firefighters responding to the area, according to Ruggiero. —Eduardo Cuevas, USA Today, 9 Aug. 2025

The Canyon Fire is burning in a mountainous area north of Los Angeles and has been spreading toward the community of Castaic in L.A. County. —Denise Chow, NBC news, 9 Aug. 2025

What To Know The Canyon Fire started at 1:25 p.m. local time in a remote mountainous area southeast of Piru Lake, north of Highway 126 and west of the town of Castaic. —Robert Birsel, MSNBC Newsweek, 8 Aug. 2025

The conflict largely centered around the status of the Nagorno-Karabakh region, a mountainous area in Azerbaijan with a majority-Armenian population, but which declared independence in 1991. —Caitlin McFall, FOXNews.com, 8 Aug. 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