spare tire vs fatty tissue

spare tire and fatty tissue both are nouns.

Word	Noun	Adjective	Verb	Adverb
spare tire	Yes	No	No	No
fatty tissue	Yes	No	No	No

As nouns, fatty tissue is a hypernym of spare tire; that is, fatty tissue is a word with a broader meaning than spare tire:

spare tire: excess fat around the waistline
fatty tissue: a kind of body tissue containing stored fat that serves as a source of energy; it also cushions and insulates vital organs

Other hypernyms of spare tire include adipose tissue, fat.

spare tire (noun)	fatty tissue (noun)
excess fat around the waistline	a kind of body tissue containing stored fat that serves as a source of energy; it also cushions and insulates vital organs