Buttery food is full of butter, a rich creamy fat. Buttery also describes anything that reminds you of butter, like warm yellow light or a smooth talker who’s trying to butter you up so she can borrow your car.
Although buttery is often used literally, as in “buttery popcorn,” it can describe anything that’s like butter in another way. If you describe someone's words or manner as buttery, you mean that they act insincerely complimentary or fawning. An old-fashioned meaning of buttery is "storeroom," like a pantry for keeping food or wine. Some British universities have a buttery, which is a snack shack for students.