Merriam-Webster Collegiate Dictionary - fester

 I. noun  Etymology: Middle English, from Anglo-French festre, from Latin fistula pipe, fistulous ulcer  Date: 14th century a suppurating sore ; pustule  II. verb  (~ed; ~ing)  Date: 14th century  intransitive verb  1. to generate pus  2. putrefy, rot  3.  a. to cause increasing poisoning, irritation, or bitterness ; rankle dissent ~ed unchecked  b. to undergo or exist in a state of progressive deterioration allowed slums to ~  transitive verb to make inflamed or corrupt