Symbol for cyclic quadrilateral Is there a symbol to denote, say, $ABCD$ is a cyclic quadrilateral? (I very much doubt it.)

$\square$ denotes a square. $\blacksquare$ is used to end proofs, mostly. It's probably not standard but you could use sonething like: $$\bigcirc\hspace{-4.4mm}\raise{-0.5mm}\square$$ \bigcirc\hspace{-4.4mm}\raise{-0.5mm}\square to denote them, if many of them are talked about. Just present the symbol meaning first.  Just put in as a definition of a newcommand in your pdf/book/article etc., so you can refer to the symbol easier. This is more of a LaTeX stackexchange question, as far as creating it. 
