I would like to know when i use "rather" in the sentences, what is the meaning of this word?

rather does sound "british" to americans, when meaning "quite/fairly" ... we tend to use "pretty" as an adverb: she is pretty tall

however, rather can also mean "instead (of)" (usually used with "than")

i would rather eat beef than chicken.
i went to spain rather than portugal.
i am spending the afternoon playing on-line rather than working.
It means quite/fairly. Rather is stronger than fairly, and often suggests that a quality is bad or unsuitable.

e.g. Although he is fairly intelligent, he behaves in a rather stupid way when he gets annoyed.

Rather sounds tipically British to most Americans. They would use fairly, somewhat or pretty instead.
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 moijelesuis's reply was promoted to an answer.
I went to Spain rather than Portugal. You mean I'd rather go to Spain than Portugal?
there is that aspect also of rather ... again, though, it means "instead of"
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