"low mountain" is a correct and usable phrase in written English.
It can be used to describe a mountain that is not very high or tall. Example: The hikers set out to climb the low mountain that stood in front of them, enjoying the scenic views and cool breeze along the way.
In the near distance stood a low mountain with a saguaro at the summit.
Winter hiking and snowshoeing trails criss-cross the low mountain areas.
From the fireplace itself was extruding what appeared to be a low mountain of black volcanic ash.
The plain rises gradually from the sea eastward to the Mayombé Massif, a low mountain range that parallels the coast.
Cradled within the Var between Fréjus and Hyères lies a bewitching hinterland, a low mountain range known in Provençal as Lei Mauro: the Sombre Ones.
In the south, two low mountain ranges, the Sierra del Tandil and the Sierra de la Ventana, extend inland from the coast in northwesterly directions.
A hike along Australia's Great Dividing Range would reveal a series of plateaus and low mountain ranges roughly paralleling the coasts of Queensland, New South Wales, and Victoria.
The relief is characterized by the low mountain ranges of the Aimorés Mountains on the western border and by isolated groups of hills on the eastern coastal plains.
For the application, an area representative of the hilly-low mountain sectors of the Italian Southern Apennines was chosen (Rivo basin, in Molise Region).
Guiana Highlands, plateau and low-mountain region of South America located north of the Amazon and south of the Orinoco River.
We examined the EMS in assemblages occupying a low-mountain river system in central Germany, sampled over three consecutive years.
