(of a disease) lasting for a long time; difficult to cure (Oxford)
British English, informal) very bad (Oxford)
(especially of a disease or something bad) continuing for a long time (Cambridge)
There is a chronic shortage of teachers. (Cambridge)
Mr. George is resigning because of chronic heart disease. (Cambridge)
chronic shortage
chronic heart disease
Sustained
Lifelong
Temporary
Inconstant
Chronicity