spare tire

noun

1. a tire used or kept available as an emergency replacement on a vehicle.

2. Informal.,  excess fat around the waistline.

Word History and Origins

Origin of spare tire¹

First recorded in 1920–25

Idioms and Phrases

Fat around one's middle, as in He's determined to lose ten pounds and that spare tire he's acquired. This expression transfers the term for an extra tire carried in cars in case of a flat tire to excess fat around the waist. [Colloquial; mid-1900s]