1. (with reference to a dead body or other organic matter) make or become rotten; decay or cause to decay: "dead plant matter can be completely decomposed by microorganisms"Similardecayrotputrefygo badgo offspoilfesterperishdeterioratedegradebreak downbreak upmoldertechnical:mortifynecrotizesphacelatearchaic:corrupt
▪ (with reference to a chemical compound) break down or cause to break down into component elements or simpler constituents:"many chemicals decompose rapidly under high temperature"Similarbreak upbreak apartfall apartfragmentdisintegratecrumbledissolvebreak downdecay
Word Originmid 18th century (in the sense ‘separate into simpler constituents’): from French décomposer, from de- (expressing reversal) + composer.