1. having many mountains; characterized by mountains
2. very large in size or amount; huge
Usage: figurative

Examples

• The mountainous region attracts many hikers each year.
• Switzerland is known for its mountainous terrain.
• We drove through mountainous countryside on our way to the cabin.
• The company faced mountainous debt after the merger.
• She had a mountainous pile of homework to complete.
• The mountainous waves crashed against the shore during the storm.