fes·ter (fstr)
v. fes·tered, fes·ter·ing, fes·ters
v.intr.
1. To generate pus; suppurate.
2. To form an ulcer.
3. To undergo decay; rot.
4.
a. To be or become an increasing source of irritation or poisoning; rankle: bitterness that festered and grew.
b. To be subject to or exist in a condition of decline: allowed the once beautiful park to fester.
v.tr.
To infect, inflame, or corrupt.
n.
A small festering sore or ulcer; a pustule.
[Middle English festren, from festre, fistula, from Old French, from Latin fistula.]