Definition of “really” - Learner’s Dictionary

really

adverb uk us /ˈrɪəli/
VERY

A1 very or very much:

She's really nice.
I really don't want to go.
That's really interesting.
"Did you like it then?" "Er, not really" (= no).
TRUTH

B1 used when you are saying what is the truth of a situation:

She tried to hide what she was really thinking.
They didn't really say anything important.
Really?

A2 used when you are surprised at what someone has just said:

"Apparently, he's leaving." "Really?"

(Definition of “really” from the Cambridge Learner's Dictionary © Cambridge University Press)