from
The Collaborative International Dictionary of English v.0.48
Deteriorate \De*te"ri*o*rate\ (d[-e]*t[=e]"r[i^]*[-o]*r[=a]t),
v. t. [imp. & p. p. {Deteriorated}
(d[-e]*t[=e]"r[i^]*[-o]*r[=a]`t[e^]d); p. pr. & vb. n.
{Deteriorating} (d[-e]*t[=e]"r[i^]*[-o]*r[=a]`t[i^]ng).] [L.
deterioratus, p. p. of deteriorare to deteriorate, fr.
deterior worse, prob. a comparative fr. de down, away.]
To make worse; to make inferior in quality or value; to
impair; as, to deteriorate the mind. --Whately.
[1913 Webster]
The art of war . . . was greatly deteriorated.
--Southey.
[1913 Webster]