Verb fatten up has 1 sense

1. fatten, fat, flesh out, fill out, plump, plump out, fatten out, fatten up - make fat or plump; "We will plump out that poor starving child"
   --₁ is one way to change, alter, modify
   Sample sentences:
   Somebody ----s something
   Somebody ----s somebody
   

fatten up

Part of Speech: Verb phrase

Senses:

1. (Transitive) To make someone or something gain weight or become fatter:

   The farmer decided to fatten up his livestock before the market season.

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2. (Intransitive) To gain weight or become fatter:

   She started to fatten up after she quit her regular exercise routine.

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3. (Transitive, figuratively) To make something more profitable or successful:

   The company launched a new marketing campaign to fatten up their profits.

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Usages:

• The chef always uses extra butter and cream to fatten up his dishes.
• The farmers fatten up their chicken before selling them for a higher price.
• After months of training, he finally fatten up and gained muscle mass.