According to La Wik, "cultural appropriation is the adoption of some specific elements of one culture by a different cultural group...It can include the introduction of forms of dress or personal adornment, music and art, religion, language, or social behavior. These elements, once removed from their indigenous cultural contexts, may take on meanings that are significantly divergent from, or merely less nuanced than, those they originally held."
Case in point:
Flash mob, Antwerp, Belgium, 23rd March 2009:
Flash mob, Kansas City, MO, USA, 10th April, 2010:
Sorry, no way to embed this video - if interested, you'll just have to follow the link. But this will give you the general idea:
(Flash mob, Philadelphia, PA, USA, 22nd March, 2010).