Recovery from illness; recuperation; convalescence; an instance of this.
In early use apparently only in the works of Coleridge..
Origin
Early 19th century; earliest use found in Samuel Taylor Coleridge (1772–1834), poet, critic, and philosopher. From classical Latin revalēscere to regain one's strength, get well again, (of consciousness) to revive (from re- + valēscere to become sound in health from valēre + -ēscere: see -escent) + -ence, probably after convalescence, reconvalescence. Compare post-classical Latin revalescentia.