HarperCollins Span-Engl unabridged:
pachuco - (Mex) a: (adj) (= llamativo) flashily dressed
b: (sm/f) 1: (pey) (= chicano) Chicano, Mexican-American
2: (= bien vestido) sharp dresser, snappy dresser

M-W:
pachuco - a young Mexican-American having a taste for flashy clothes and a special jargon and usually belonging to a neighborhood gang
http://www.merriam-webster.com/dictionary/pachuco

Wikipedia:
Pachuco refers to a particular old school subculture of Chicanos and Mexican-Americans associated with zoot suits, street gangs, nightlife, and flamboyant public behavior. The idea of the pachuco – a zoot-suited, well-dressed, street-connected flamboyant playboy of Hispanic/Latino heritage – originated in El Paso, Texas, and Ciudad Juárez, Mexico, [and] moved north, following the line of migration of Mexican railroad workers ("traqueros") into Los Angeles, where it developed further. ...
The origin of the term "pachuco" is uncertain, but one theory connects it to the city of El Paso, Texas, which was sometimes referred to as "Chuco Town" or "El Chuco." People migrating to El Paso would say, in Spanish, that they were going "pa' El Chuco." These migrants became known as pachucos.[1] ...
Pachucos called their slang Caló (sometimes called "pachuquismo"), a unique argot that drew on the original Spanish Gypsy Caló, Mexican Spanish, the New Mexican dialect of Spanish, and American English ...
Pachuco culture in America was at its height during World War II ... flashy zoot suits were seen as unpatriotic by other Americans. ...
https://en.wikipedia.org/wiki/Pachuco

Dictionary.com:
pachuco - (especially among Mexican-Americans) a teenage youth who belongs to a street gang known for its flamboyant style.
http://www.dictionary.com/browse/pachuco

Collins:
pachuco - a young Mexican living in the US, esp one of low social status who belongs to a street gang
http://www.collinsdictionary.com/dictionary/e...

Oxford:
pachuco -
Mexico (informal)
1: [persona] Que es feo y se viste mal.
Mexico (informal)
1: Joven de origen mexicano, de clase social baja, que vivía en las ciudades del sur de Estados Unidos de América en la década de 1950 y que se caracterizaba por defender su identidad como grupo social frente a las costumbres estadounidenses
https://es.oxforddictionaries.com/definition/...

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