A blouse is a shirt usually worn by a woman. Your grandmother's favorite silk blouse might have pearl buttons down the front.
A dressy item of clothing worn on the top of the body, mainly by girls or women, is sometimes called a blouse. Some military and historical garments are also blouses, and you can use the word as a verb meaning "to puff out or hang in folds," the way many blouses do. In French the word means "workman or peasant's shirt," but beyond that its origin is mysterious.