■ verb [often as adjective ~ing ]
1》 (of a wound or sore) become septic.
↘(of food or rubbish) become rotten.
2》 (of a negative feeling or a problem) intensify, especially through neglect.
3》 deteriorate physically and mentally in isolated inactivity.
Origin
ME: from ~ 'fistula', later '~ing sore', or OFr. festrir (v.), both from OFr. festre (n.), from L. fistula 'reed, fistula'.