In science fiction stories, a skimmer is a hovercraft-like vehicle, usually supported by anti-grav. There is wide variation in skimmer design, what with being immaginary and all. They often look like cars without wheels, but in Star Wars they look like little space ships.
In real life, a skimmer is a light, usually straw hat with a stiff wide brim and a flat shallow crown. (See: panama hat, Boater).