When you have that extra bit hanging over your belt....another word for muffin top.
Marie: I like them jeans on her.
Emma: eww no look at the spare tyre hanging over the top in all its mushy greatness.
Marie: yeah you're right they'd look so much better on me hohoho!
the definition of spare tyre - when the female or male uses the female or male when either are feeling down. ( for example, when the tyres flat on a vehicle, you only use it when you need to ).
or - the person uses one another when he or she only needs or wants something
she's treating me like a spare tyre