A suspender is a strap that holds your pants up. If your jeans are too big for you, you might try wearing some colorful suspenders.
Suspenders almost always come in a pair. They are an alternative to a belt—instead of looping around your waist, suspenders are worn over your shoulders, clipping to the waistband of your pants at the front and the back. Suspenders is an American English word, coined in the early 19th century from the verb suspend, "to hang."