mountain
n. countable A1 Beginner Oxford US //ˈmaʊntən// UK //mˈaʊntɪn// moun·tain
n. a very high piece of land with steep sides. It is much taller than a hill.
n. a large natural elevation of the earth's surface rising abruptly from the surrounding level. Often used figuratively to describe a large pile or quantity of something.
We climbed the mountain during our summer holiday.
The hikers reached the top of the mountain just as the sun began to set over the valley.
Geological forces over millions of years pushed the earth's crust upward to form this mountain range, which now serves as a natural border between the two nations.
Usage
Often used with the preposition 'of' when describing a large quantity, such as 'a mountain of paperwork'.