Noun | 1. | retrogression - passing from a more complex to a simpler biological form abiotrophy - a loss of vitality and a degeneration of cells and tissues not due to any apparent injury cataplasia - (biology) degenerative reversion of cells or tissue to a less differentiated or more primitive form |
2. | retrogression - returning to a former state reversal - a change from one state to the opposite state; "there was a reversal of autonomic function" |