ROmega

ROmega is suggestion for the Latex notation

\documentclass{article}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage{relsize}
\newcommand{\rOmega}{\mathbin{\rotatebox[origin=c]{180}{$\Omega$}}}
\DeclareMathOperator*{\bOmega}{\mathlarger{\mathlarger{\mathlarger{\Omega}}}}
\DeclareMathOperator*{\ROmega}{\mathlarger{\mathlarger{\mathlarger{\rOmega}}}}
\begin{document}
$A \rOmega B$
\begin{eqnarray}
\bOmega_a^b
\end{eqnarray}
\begin{eqnarray}
\ROmega_a^b
\end{eqnarray}
\end{document}