IPA: //ˈfætɪst//
KK: /ˈfætɪst/
The highest degree of being overweight or having a lot of body fat compared to others.
He is the fattest person in the competition.
Comparative: fatter
Superlative: fattest
Fattest → It is formed from "fat" (from Old English *fǣtt*, meaning having a large amount of body fat) and the suffix "-est" (meaning the most). The word "fattest" describes the state of having the most fat compared to others.
Think of 'fat' as having a lot of body fat, and '-est' means the most. So, 'fattest' means having the most fat.