fester(noun, verb) noun1. a sore that has become inflamed and formed pusDefinition categories: state, sore verb1. ripen and generate pus- her wounds are festeringSimilar word(s): maturate, suppurateDefinition categories: body, discharge, eject, exhaust, expel, releaseSentences with fester as a verb:- Deal with the problem immediately; do not let it fester.