Streetwise describes a person who knows how to stay safe and get by in a city, especially in the rougher parts of one. A streetwise person can tell when someone is trying to trick them, knows which streets to avoid at night, knows how to talk to people so that trouble does not start. It is knowledge you get from living in a place, not from books or school. Because of that, it is often used against book learning: you can say someone has a lot of degrees but is not very streetwise, and everyone understands you mean they are clever but easy to fool. It is a compliment almost every time it is used. The picture behind the word is a young person who grew up in a hard neighbourhood and came out sharp, not a criminal. British English also has 'street-smart' borrowed from American English, and Americans say 'street-smart' more often than 'streetwise'. Though actually the word has softened a lot in recent years. Companies now say things like 'a streetwise young brand' or 'a streetwise business decision', meaning only 'practical and sharp, not naive' — no city and no danger left in it at all. If you meet it in an advertisement, read it that looser way.