From mountain + -ous after Middle French montagneux, from Late Latin montāniōsus, from montānia, from Latin mons.

• (RP, America) IPA: /ˈmaʊn.tɪn.əs/
• (<>, <>; <> with <>) IPA: /ˈmaʊn.tən.əs/, [ˈmæʊn.tn̩.əs], [-ʔn̩-], [ˈmæ̃ʊ̃(n)-]

mountainous

1. Having many mountains; characterized by mountains; of the nature of a mountain; rough (terrain); rocky.
   • 1705, George Cheyne, “Of the Existence of a Deity”, in Philosophical Principles of Natural Religion: […], London: […] George Strahan […], →OCLC ↗, § XXIX, page 184 ↗:

     [Water vapour bubbles] hit againſt the ſides of the more eminent and Mountainous Places, of the Globe, and by this Concuſſion are condenſed, and thus become heavier than the Air they ſvvom in, and ſo gleet dovvn the rocky Caverns of theſe Mountains, […]

2. Resembling a mountain, especially in size; huge; towering.
3. (figurative, of a problem or task) Very difficult.
4. (obsolete) Inhabiting mountains; hence, barbarous.

• See also Thesaurus:large

• French: montagneux
• German: bergig, gebirgig
• Italian: montagnoso, montuoso
• Portuguese: montanhoso
• Russian: гори́стый
• Spanish: montañoso

• Russian: гороподобный