Symbol about not orthogonality in LaTeX

To negate the \perp (perpendicular) symbol, the command \not\perp provides a simple solution, but this negated symbol doesn't look that great IMHO:

If you load the mathabx package, you get the command \notperp which looks pretty good, as does now the output of \not\perp. The same effect can be achieved if you load either the MnSymbol package or the fdsymbol package and use the command \notperp (same name used by both packages). Notice, though, that even if you load the MnSymbol of the fdsymbol package, the output of \not\perp still looks pretty bad, i.e., as bad as if you hadn't loaded any extra package at all.

Addendum: Following a request by the OP, here's an MWE that shows how to load the mathabx package and generate the symbol using the package's \notperp macro, as well as with \not\perp"

\documentclass{article}
\usepackage{mathabx}
\begin{document}
$a \notperp b$, $c \not\perp d$
\end{document}

---

Next, here's an MWE that shows the use of the MnSymbol package to generate these symbols:

\documentclass{article}
\usepackage{MnSymbol}
\begin{document}
$a \nperp b$, $c \not\perp d$
\end{document}

---

Finally, with the use of the fdsymbol package and its \nperp macro:

\documentclass{article}
\usepackage{fdsymbol}
\begin{document}
$a \nperp b$, $c \not\perp d$
\end{document}

---

Happy TeXing!

You can add a \not in front of it:

a \not\perp b

This gives you a struck through orthogonal symbol.