to make or become worse or inferior in character, quality, value, etc.
to disintegrate or wear away.
Origin of deteriorate
1565–75; < Late Latindēteriōrātus made worse (past participle of dēteriōrāre), equivalent to Latindēterior worse (dē from + -ter- formative in adjectives of spatial orientation (cf. exterior, interior) + -ior comparative suffix) + -ātus-ate1
Related formsde·te·ri·o·ra·tive, adjectiveun·de·te·ri·o·rat·ed, adjectiveun·de·te·ri·o·rat·ing, adjectiveun·de·te·ri·o·ra·tive, adjective
1640s (as a past participle adjective, 1570s), from Late Latin deterioratus, past participle of deteriorare "get worse, make worse," from Latin deterior "worse, lower, inferior, meaner," contrastive of *deter "bad, lower," from PIE *de-tero-, from demonstrative stem *de- (see de). Originally transitive in English; intransitive sense is from 1758. Related: Deteriorated; deteriorating.