1N-COUNT 备用轮胎 A spare tyre is a wheel with a tyre on it that you keep in your car in case you get a flat tyre and need to replace one of your wheels. 备用轮胎
2N-COUNT (人的腰腹部的)一圈赘肉 If you describe someone as having a spare tyre, you mean that they are fat around the waist. (人的腰腹部的)一圈赘肉 [mainly British, informal]