to fall below a normal or desirable level in physical, mental, or moral qualities; deteriorate: The morale of the soldiers degenerated, and they were unable to fight.
to diminish in quality, especially from a former state of coherence, balance, integrity, etc.: The debate degenerated into an exchange of insults.
Pathology. to lose functional activity, as a tissue or organ.
Evolution. (of a species or any of its traits or structures) to revert to a simple, less highly organized, or less functionally active type, as a parasitic plant that has lost its taproot or the vestigial wings of a flightless bird.
to cause degeneration in; bring about a decline, deterioration, or reversion in.