downgrade

Short definition from Wiktionary

Noun

1. 1
   A reduction of a rating, as a financial or credit rating.
2. 2
   A downhill gradient on a road or railway.
3. 3
   A reduction in quality; a descent towards an inferior state.

Verb

1. 1
   To place lower in position.
2. 2
   To reduce in complexity, or remove unnecessary parts; to dumb down.
3. 3
   To disparage.
4. 4
   to reduce the official estimate of a storm's intensity.
5. 5
   To revert software back to an older version.