Unnamed
public text v1 · immutable
[Unimportant things]
\theoremstyle{definition}
\newtheorem{definition}{Definition}
\newcommand{\bdefbs}[1]{\begin{definition}[{#1}]\\} % <- This line cannot be broken.
\newcommand{\edefbs}{\end{definition}\begin{flushright} $\mathop{\bigstar}$ \end{flushright}}
\begin{document}
\bdefbs
Here I write some definition.
\edefbs
\end{document}