The phrase "a massif" is correct and usable in written English.
It is typically used in geological or geographical contexts to refer to a large mountain mass or a compact group of mountains.
Example: "The Mont Blanc massif is one of the most famous mountain ranges in the Alps."
Alternatives: "a mountain range" or "a mountain block".
A massif (1,798 m) commanding the Lake of Lucerne.
It became clear that Mulanje is a massif, not just one mountain.
The converter is in fact a single-phase transformer with a massif secondary winding, calculated to work in short-circuit but in a stabilized thermal regime.
The Hindu Kush, a massif of snow and ice, loomed 30 miles to the north; Kabul lay far below us, obscured behind a layer of dust and smoke that smudged the panorama like a dirty fingerprint.
So I crossed the Monti Martani (a massif best known as the epicenter of the earthquake that toppled the ceilings of the Basilica of St. Francis of Assisi in 1997) to consult with my friends Joanna Ross and Bruce Adgate.
The Troodos is a massif of eroded igneous rock dissected by steep valleys covered with stands of pine, cypress, dwarf oak, and cedar, now protected as state forests; its peaks are snow-clad from December to March.
I'd never seen anything like it, an awesome massif, a clump of peaks, an agglomeration of several mountains.
Jebel Marra, in the centre of Darfur, is a volcanic massif with an estimated 1,500 towns, villages and hamlets.
From there Scott, Wilson and Shackleton gazed south across the glacier to a spectacular massif, rising to an elevation of 14,042 feet through an intricate system of ridgelines that converge on its lofty summit.
The Fujian-Zhejiang section forms a part of a raised massif that has been subjected to folding and refolding.
Despite the army's efforts, it retains a base at Sumapaz, a mountainous massif to the south that lies within the capital's administrative boundary.
