- fatten⇄fatten, transitive verb.
1. Also, fatten up. to make fat; feed (animals) for market.
Ex. The farmer fattened his pigs for market.
2. to make productive; enrich (soil).
3. (Figurative.) to fill or build up; increase in size.fatten⇄noun fattener.fatten⇄v.i. to become fat.
Ex. The pigs fattened on corn. The meanest worm That ... fattens on the dead (Shelley).