A gauzy fabric is sheer and lightweight. You might have gauzy curtains that allow light to shine through them as they blow in the breeze.
Use the adjective gauzy to describe something light and translucent. A girl's curtain of long hair and her summery cotton dress might both be gauzy. The word comes from gauze, which is a light, filmy fabric made of a thin, sheer material. The French root is gaze, which in turn comes either from the Arabic gazz, "raw silk," or possibly from the city of Gaza, where this type of fabric is made.