The word "fart" is generally considered rude in most social contexts.
While it's a perfectly natural bodily function, the word itself is often used in a humorous or vulgar way.
It's important to be mindful of the audience and setting when using this word. In casual settings with close friends, it might be acceptable, but in formal settings or around strangers, it's best to avoid using it.
There are many other ways to express the same concept without using such a direct and potentially offensive term.
Ultimately, whether or not "fart" is considered rude depends on the specific context and the individuals involved.