A (usually male) native or inhabitant of Buenos Aires.
Usually with lower-case initial. Of or relating to the natives or inhabitants of Buenos Aires.
Early 19th century; earliest use found in The Times. From American Spanish porteño of or relating to the Argentinian capital city Buenos Aires (or to any of a number of other cities which have a port or which have Spanish puerto in their name), (as noun) native or inhabitant of this city from puerto + -eño, suffix forming nouns and adjectives from place names.