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]