Fatten

Verb

1. To cause (a person or animal) to be fat or fatter.

   "We must fatten the turkey in time for Thanksgiving."

2. To become fat or fatter.

   "He gradually fattened in the five years after getting married."

3. To make thick or thicker (often something containing paper, especially money).
4. To become thick or thicker.
5. To make (soil) fertile and fruitful.

   "to fatten land"