A genericized trademark is a brand name that has become synonymous with the class of product iteslf.  A few well-known genericized trademarks that have lost their legal protection are yo-yo (originally trademarked by Duncan), zipper (originally trademarked by B.F. Goodrich), and trampoline (for the generic “rebound tumbler”).  A trademark becomes genericized typically after it achieves dominance in a specific market.  There are also trademarks that are still legally protected, even though their brand names have become colloquial.  This list includes Band-Aid (adhesive bandage), Crock-Pot (slow cooker), Kleenex (facial tissue), Rollerblades (in-line skates), and Styrofoam (extruded polystyrene foam).  I didn’t know Styrofoam was a brand name, I grew up just calling it extruded polystyrene foam.