from Wiktionary, Creative Commons Attribution/Share-Alike License
- v. to make something worse
- v. to deteriorate
from the GNU version of the Collaborative International Dictionary of English
- transitive v. To make worse; -- the opposite of improve.
- intransitive v. To grow worse; to deteriorate.
from The Century Dictionary and Cyclopedia
- To render worse; injure the quality of.
- To grow worse.
dis- + improve (Wiktionary)