cowboys and guachos
Literally it means orphan, but it's commonly used to say "small kid" like in "De quién son estos guachos?" (Who's kids are these?), "guy" like in "Qué hacés, guacho?" (How are you, men?), "mean" like in "No seas guacho" (Don't be mean) or to express envy or disapproval like in "Es un guacho!" (He's a guacho!). It is rarely used with it's original meaning "orphan", for which the word "huérfano" is commonly used. Not to be confused with gaucho, which is the Argentine equivalent of a cowboy.