v. & n.
--v.intr. (usu. foll. by into) fall back or sink again (into a worse state after an improvement).
--n. also the act or an instance of relapsing, esp. a deterioration in a patient's condition after a partial recovery.
Phrases and idioms:
relapsing fever a bacterial infectious disease with recurrent periods of fever.
Derivatives:
relapser n.
Etymology: L relabi relaps- (as RE-, labi slip)