mountainous

adjective

moun·​tain·​ous ˈmau̇n-tə-nəs 

ˈmau̇nt-nəs

1

: containing many mountains

2

: resembling a mountain : huge

mountainously adverb

mountainousness noun

Synonyms

• astronomical
• astronomic
• Brobdingnagian
• bumper
• colossal
• cosmic
• cosmical
• cyclopean
• elephantine
• enormous
• galactic
• gargantuan
• giant
• gigantesque
• gigantic
• grand
• herculean
• heroic
• heroical
• Himalayan
• huge
• humongous
• humungous
• immense
• jumbo
• king-size
• king-sized
• leviathan
• mammoth
• massive
• mega
• mighty
• monster
• monstrous
• monumental
• oceanic
• pharaonic
• planetary
• prodigious
• super
• super-duper
• supersize
• supersized
• titanic
• tremendous
• vast
• vasty
• walloping
• whacking
• whopping

Examples of mountainous in a Sentence

the seemingly mountainous obstacles he had to overcome while growing up

Recent Examples on the Web

The drone used its thermal technology and other powerful sensors to scan the mountainous terrain where the helicopter went down amid pitch darkness and adverse weather conditions. —Paul Iddon, Forbes.com, 6 Apr. 2025

Troops easily invaded Phnom Penh, causing high-ranking Khmer Rouge to flee to western Cambodia’s mountainous terrain along the Thai border. —Ray Cavanaugh, Chicago Tribune, 3 Apr. 2025

Faezeh, 25, is a midwife who had worked in a clinic in an isolated, mountainous district of the western province of Herat. —Khwaga Ghani, NPR, 31 Mar. 2025

Set amid the rolling slopes of the Jura, a mountainous region in eastern France, the movie traces a teenager’s progression from carefree, at times careless youth to adulthood after a life-altering tragedy. —The New York Times, New York Times, 28 Mar. 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