having sunk to a condition below that which is normal to a type; esp having sunk to a lower and usu morally or physically peculiarly corrupt state

said of a plant or animal: having lost an ancestral structure, function, etc; e.g. loss of gut and eyes in tapeworm

to pass from a higher to a lower statetype or condition; to deteriorate

The road degenerated into a bumpy track

to decline from a former thriving or healthy condition

said of organisms: to evolve into a less complex form