Redefine environment to be a synonym for another

This should work:

\renewenvironment{description}{%
    \begin{LaTeXdescription}%
}{%
    \end{LaTeXdescription}%
    \ignorespacesafterend%
}

It depends a bit on how you define , specifically whether you define it in terms of the existing description but assuming LaTeXdescription is not defined to expand to something involving description you should be able to do

\let\description\LaTeXdescription
\let\enddescription\endLaTeXdescription