What is the meaning of really?

adverb

• In accordance with truth or fact or reality.
  • usage: "she was now truly American"; "a genuinely open society"; "they don't really listen to us"
  • synonyms: truly, genuinely
• In actual fact.
  • usage: "to be nominally but not actually independent"; "no one actually saw the shark"; "large meteorites actually come from the asteroid belt"
  • synonyms: actually
• In fact (used as intensifiers or sentence modifiers. )
  • usage: "in truth, moral decay hastened the decline of the Roman Empire"; "really, you shouldn't have done it"; "a truly awful book"
  • synonyms: in truth, truly
• Used as intensifiers; `real' is sometimes used informally for `really'; `rattling' is informal.
  • usage: "she was very gifted"; "he played very well"; "a really enjoyable evening"; "I'm real sorry about it"; "a rattling good yarn"
  • synonyms: very, real, rattling