fatten up
phrasal verb.phrasal verb. to make a person or animal gain weight, often by giving them a lot of food.
phrasal verb. to increase the body mass or fat content of a person or animal through deliberate overfeeding; often used in agricultural or caregiving contexts.
The farmer is trying to fatten up the cows for winter.
My grandmother always tries to fatten me up with her homemade pies whenever I visit.
The livestock were moved to the lower pastures to fatten up on the lush spring grass before being sent to market.
can be used for animals (literal) or people (often slightly humorous or affectionate).
this is a transitive phrasal verb that can be separated by the object; it follows the pattern of 'adjective + en' verbs like 'shorten' or 'widen' combined with the particle 'up' to show completion.
He wants to fat up the bird.He wants to fatten up the bird.the verb is 'fatten' (to make fat), not the adjective 'fat'.
Last updated April 24, 2026