ขี้ [khîi] literally means excrement and it’s not a very polite word when used on its own. It’s actually more like the word “sh*t” in English.
But it is commonly used to describe everyday bodily secretion such as:
Using it in this context is totally fine and not impolite as when used on its own.
Apart from that meaning, we also have many common adjectives that start with the word ขี้[khîi] to describe things which are mostly negative.
Some examples of person related adjectives that begin with ขี้[khîi] :