Cultural appropriation is defined by Wikipedia as "a concept in sociology dealing with the adoption of the elements of a minority culture by members of the dominant culture."
You've probably heard the term thrown around a lot. Like when these two white woman shut down their burrito cart after they were accused of stealing recipes from a Mexican community and not attributing them to the original chefs.
Usually there's an element of profiting off of a marginalized cultural group you "don't belong to" that grinds people's gears. Like when the Kardashian sisters begin rocking popular Black hairstyles and fashions, or when white pop stars embrace influences from hip hop and R&B culture, then turn country all of a sudden, like Justin Timberlake and Miley Cyrus have been accused of doing.