fatten

fatten — verb

1. to cause a person, animal, or thing to become heavier or rounder by feeding them

1.verbtransitive / intransitiveB1
Definition

to cause a person, animal, or thing to become heavier or rounder by feeding them well; or to become heavier and rounder oneself, especially with the purpose of reaching a healthy or desired size.

Example

The farmer fattened the pigs over the winter for the autumn market.

transitive: fatten + animal for a purpose

Mark tried to fatten up his rescue dog after finding her on the street.

phrasal: fatten up + object for recovery

Common collocations
  • fatten cattle/pigs/livestock/sheep
  • fatten up a sick child
  • fatten on grass/grain/pasture
  • fatten one's wallet/account/savings
  • fatten a budget/proposal/report
Synonyms
  • plump

    gentler and more specific to rounding out, often used for babies or cheeks

  • fatten up

    phrasal verb, more colloquial; implies bringing to a full/healthy size

  • feed up

    British English; focuses on giving extra food to restore strength

Antonyms
  • thin

    to make or become thinner

  • slim down

    phrasal verb focusing on intentional weight reduction

Grammar Patterns

fatten + object (animal, person, thing)

fatten + object + up

fatten on + food/pasture

Usage Note

The particle 'up' (fatten up) is common in everyday speech and adds a sense of 'fully' or 'completely' — e.g., fatten up a sick child, fatten up a thin calf. Figuratively, fatten can refer to increasing the size or amount of something non-physical, such as a bank account, budget, or document. In these uses the transitivity is always active (transitive); the intransitive pattern (fatten on + food) is restricted to animal subjects.

Common Mistakes

I want to fatten my body at the gym
I want to build muscle at the gym
'fatten' implies gaining fat or weight through eating, not building muscle through exercise.
She fattened on the couch watching TV
She got fat from sitting on the couch watching TV
'fatten on' is used for animals eating pasture, not humans in informal contexts.

Word family

Synonym discussion

Sense: verb/1

Fatten is the most general verb for making a living thing heavier by feeding it well, and it can extend figuratively to savings or documents. Plump carries a gentler, more affectionate tone — you plump up a pillow or a baby's cheeks, but you do not plump livestock for slaughter. Fatten up is a common phrasal alternative that emphasizes reaching a full or healthy size, often used with pets or people recovering from illness. Feed up is mainly British English and focuses on providing extra nourishment rather than on the resulting size. For example, a farmer fattens pigs for market, a grandmother feeds up a thin grandchild, and a mother plumps a baby's cushion.

fatten ↗plump ↗fatten upfeed up ↗

Common collocations

Nouns

Adverbs

Phrases

  • fatten up
  • fatten on pasture
  • fatten for market
  • fatten the bottom line

Prepositions

Etymology

Old EnglishMiddle EnglishEnglish

Fatten comes from Middle English fattenen, which developed from Old English fǣtnian — a verb built on the adjective fǣtt (meaning 'fat'). The word has been used since before the 12th century for the literal feeding of animals, with figurative uses for money and accounts appearing in the 17th century.