LaTeX Forum

%
\newglossaryentry{Perm}{name=\ensuremath{{\epsilon}},description={Complex relative permittivity of a material}}

\newglossaryentry{Perm}{name=\ensuremath{\underline{\epsilon}},description={Complex relative permittivity of a material}}

% Ende des Dokumentes 

\documentclass{scrartcl}
\usepackage[nopostdot]{glossaries}

\newcommand\robustunderline{}
\DeclareRobustCommand\robustunderline[1]{\underline{\ensuremath{#1}}}

\makeglossaries

\newglossaryentry{Perm}{
	name=\robustunderline{\epsilon},
	description={Complex relative permittivity of a material}
}

\begin{document}
\gls{Perm}
\printglossary
\end{document}