IPA: /ˈfætənər/
KK: /ˈfætənər/
A person or thing that makes something or someone gain weight or become fatter.
The farmer used a fattener to help the livestock grow larger and healthier.
Fattener → It is formed from "fat" (from Old French *fat*, meaning having a lot of fat or flesh) and "-en" (a suffix used to form verbs indicating to make or become). The word "fattener" means to make something fat or to cause it to gain weight.
Think of the word 'fat' which means having a lot of flesh, and remember that 'fattener' is something that makes something else become fat.