- 1[intransitive] (of a wound or cut) to become badly infected festering sores/wounds If you don't take the splinter out, it will fester.
- 2[intransitive] (of bad feelings or thoughts) to become much worse because you do not deal with them successfully Instead of talking the matter over with him, she allowed her resentment to fester in her mind.
NAmE//ˈfɛstər//Verb Forms present simple I / you / we / they fester
he / she / it festers
past simple festered
-ing form festering