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

At the time, central Appalachia was widely depicted in the popular press as a backward, ignorant region whose mountainous terrain kept its people isolated, outside the flow of progress – a stereotype still common today. —The Conversation, 7 Oct. 2025

These historic mines offer great mountainous lookouts. —Paige Moore, AZCentral.com, 7 Oct. 2025

In 2023 and 2024, California experienced above-average snowpack due to the frequent occurrence of atmospheric rivers, which brought heavy precipitation to the mountainous regions. —Anna Skinner, MSNBC Newsweek, 6 Oct. 2025

The terrain was steep and mountainous, the forests were thick, and threats from buffalo and leopards lurked in the wilderness. —Julia Jacobo, ABC News, 1 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