Decay in dreams is evidence of the natural cycle of life: growth, decline and regeneration. Out of decay comes new growth and knowledge. When something is decaying it is running out of energy. For it to appear in dreams indicates we must be prepared to allow things to run their natural course. Putrefaction is when the process of decay has gone past the point of no return. In mundane terms, we have a situation in our lives - perhaps a work project or a relationship - that has come to a natural conclusion and does not need to be nurtured. The experience we have gained, however, can be put to good use. You might also like to consult the entry for Mould/Mouldy.