Defined: to make or become worse; lower in quality or value; depreciate INTRANSITIVE VERB
Deterioration can be both physical and existential. An old house is deteriorating when it is in grave disrepair. A situation would be deteriorating when more and more negative or disastrous events continue with no respite.
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Definitions: v. de·te·ri·o·rat·ed, de·te·ri·o·rat·ing, de·te·ri·o·rates
v.tr. To diminish or impair in quality, character, or value: Time and neglect had deteriorated the property.
v.intr. 1. To grow worse; degenerate: The weather deteriorated overnight. His health had deteriorated while he was in prison.
2. To weaken or disintegrate; decay: The nation’s highways are deteriorating at a rapid pace.
atrophy, crumble, decay, decline, degenerate, descend, devolve, ebb, regress, retrograde, rot, sink, worsen, go to pot, go to seed