There's no strict definition of how big a hill needs to be to become a mountain, but generally, a mountain is a landform that rises significantly above its surroundings, usually with a peak, and is formed by tectonic activity or volcanic eruptions.

Here are some other terms used for large hills depending on their specific characteristics:

* Butte: A hill with a flat top and steep sides.

* Mesa: A large, flat-topped hill with steep sides, often formed by erosion.

* Hill: Can be used for a very large hill, but it usually refers to a smaller, less prominent landform than a mountain.

Ultimately, the distinction between a hill and a mountain is somewhat subjective and often depends on local usage and cultural perception.