mountainous

adjectives

having hills and crags
"hilly terrain"
is derived from
like a mountain in size and impressiveness
"mountainous waves"; "a mountainous dark man"
is similar to
above average in size or number or quantity or magnitude or extent
"a large city"; "set out for the big city"; "a large sum"; "a big (or large) barn"; "a large family"; "big businesses"; "a big expenditure"; "a large number of newspapers"; "a big group of scientists"; "large areas of the world"
containing many mountains
is derived from
is similar to
used of high or hilly country