A label jockey is someone who wont wear clothes unless they have some type of brand name "label" on them, abercrombie, hollister, north face, ect. wearing the clothes is what makes them a "jockey" of the brand. their items of clothing will usually have the name of the company clearly shown. Label jockies are usually rich suburban kids whose parents will buy them whatever they want.
look at that label jockey, her shoes are birkenstocks, her jeans are abercrombie, her shirt is hollister and her bag is gucci.