Polystyrene beads are tiny, round balls made from a type of plastic called polystyrene. They are often used for packaging materials, cushioning, and insulation because they are lightweight and can fill spaces easily. Full definition
This chunky fashionable range of pouffes is hand knitted with polystyrene beads filling. (homescapesonline.com)
Those exposed to high levels of polystyrene beads did not alter their movements at all. (sciencenewsforstudents.org)
They then filled them with tiny polystyrene beads in a soap solution to mimic dirt particles on a fabric that has gone through a wash. (newscientist.com)