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

In classical antiquity, the mountainous region was notorious for bandits; in modern times, blood feuds among clans were rife. —Literary Hub, 22 Oct. 2025

That much rain over mountainous terrain in the area could trigger catastrophic flash flooding and landslides. —Briana Waxman, CNN Money, 22 Oct. 2025

Even a weak storm could dump a ton of rain on the mountainous island of Hispaniola, potentially setting off life-threatening mudslides and flash flooding. —Jacqueline Charles, Miami Herald, 22 Oct. 2025

This story of a logger (Joel Edgerton) working in the mountainous West as early-20th-century progress rolls over him like a wonder and a curse is the one movie in the streamer’s roster of Oscars hopefuls that people seem actually to love. —Joe Reid, Vulture, 17 Oct. 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