Origin: Latin suffix -ous
Mountainous has 4 different meanings across 1 category:
containing many mountains
"The map showed that the entire northern region was mountainous, making it impossible to drive through without a 4x4 vehicle."
Having many mountains; characterized by mountains; of the nature of a mountain; rough (terrain); rocky.
"The hike up the mountainous trail was grueling because every step required us to navigate steep, rocky slopes."