A homophone is a word that sounds the same as another word, but has a different meaning and spelling. While "mountain" is a noun referring to a large landform, there is no other common word that sounds exactly the same.
However, some words come close in pronunciation:
* "mountian" is a common misspelling of "mountain," sounding very similar.
* "mounting" is a verb that can sound similar depending on the speaker's accent.
So, while there's no perfect homophone for "mountain," these words can sound similar depending on the context and pronunciation.