To refuse is to decline, deny, reject, or resist. If a stranger offers you candy, you should politely refuse.
As a noun, refuse (pronounced REF-yooss) is food waste, scraps, or garbage. As a verb, refuse (pronounced ree-FYOOZ) means to reject. If you’re mad at me, you’ll probably refuse my invitation to hang out. If your fashion sense isn't up to date, the bouncer at an exclusive nightclub might refuse entry to you. If you’re sick and you need a kidney transplant, your doctor will give you drugs to stop your body from refusing the donor kidney.