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

Two weeks into fighting, the unforgiving mountainous terrain, heavy Saudi and government air power, and a reenergized anti-Houthi coalition have kept the Houthi advance in check, preventing a collapse on the level of that in mid-September. — Brady Knox, The Washington Examiner, 4 Oct. 2026

The Los Angeles County Sheriff’s Department issued evacuation orders for the remote mountainous area northeast of Santa Clarita on Saturday afternoon. — Susanne Rust, Los Angeles Times, 4 Oct. 2026

Poppe described seeing one of PG&E’s workers being lowered by rope from a helicopter onto a transmission tower in mountainous California. — Nick Lichtenberg, Fortune, 30 Sep. 2026

The man, whose identity was withheld until his family could be notified, fatally plunged from a mountainous area of Hyrum, Utah, east of Millville Canyon and east of the small city of Millville, Cache County Chief Sheriff’s Deputy Doyle Peck said. — Dennis Romero, NBC news, 28 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