v. i. To grow worse; to deteriorate. [ 1913 Webster ]

v. t. To make worse; -- the opposite of improve. [ R. ] Jer. Taylor. [ 1913 Webster ]

n. Reduction from a better to a worse state; as, disimprovement of the earth; specific features which are worse than former features; disimprovements in the new Windows operating system. [ 1913 Webster +PJC ]