Appropriation is a Visual Arts term and refers to the creation of new art work that uses borrowed elements from another artist or culture.Most painting are Appropriation, because it very rare for someone to create something original without using a percific art style e.g. pop art or a culture e.g. African or aborignial culture.
On Wikipedia, it is also defined as the adoption, borrow, recycle or sample of aspects of man made visual culture.
Some examples/strategies of Appropriation are: imitation; karaoke; allusion; echo; mimicry, etc.
Some artists who use appropriation are: Andy Warhol, Morimura, etc.