What is the meaning of Sério?

alternative form of seriós

serious; solemn (without humor or expression of happiness)

serious (leaving no room for play; needing great attention)

dangerous

which can’t be joked about; no laughing matter

grave

concerning serious matters

a game in which two people stare at each other and the first one to laugh loses

really? (indicating surprise at, or requesting confirmation of)

Source: wiktionary.org