From Longman Dictionary of Contemporary Englishmountainsidemoun‧tain‧side /ˈmaʊntənsaɪd $ ˈmaʊntən-/ noun [countable] DNthe side of a mountain Great rocks rolled down the mountainside.
Examples from the Corpus
mountainside• A plain stone cabin, on a mountainside.• Beyond the back door was a view of mountainsides in the moonlight.• Some of the farms are on remote mountainsides.• BIn the far distance, the flames licked their way toward the beach like lava coming down the mountainsides.• Then, as the years rolled by, more bikes rolled off the edge or into the mountainside.• Round the bend ahead the road ran fairly straight, a narrow ledge cut out of the mountainside.• A grotto had been hollowed out of the mountainside, with a beautiful figure of Mary.• Jane contemplated throwing on her clothes and leaving her refuge to climb farther up the mountainside to the caves.• Wheatfields, cultivated high up the mountainsides, were lightly tinged with yellow, proclaiming the nearness of summer. 