Feather in a Cap is an idiom that is used to describe an accomplishment or achievement that is particularly impressive. The term can be broken down into two parts: feather and cap. A feather is a light, fluffy object that is often associated with birds, while a cap is a type of headwear. Together, the phrase implies that the accomplishment is so impressive that it is like having a feather in one's cap. The crossword solution for this term is PLUME, which is a type of feather.