Porteño Spanish is the dialect of caste-sha-no (castellano) spoken in Buenos Aires, Argentina and the surrounding areas. It is categorized by an Italian-like pronunciation and colorful Lunfardo slang.Browse Slang Dictionary
Usually this is used to describe smart, capable people. The originally meaning is "rope", but it is used in the same way "sharp" is used to describe someone in English.
In Chile, "piola" is used to describe low-key, quiet people.