documentclass{article}
usepackage{amsmath,stackengine}
defprf{ensurestackMath{mathbin{stackengine{-.5pt}{-}{.}{O}{c}{F}{F}{S}}}}
begin{document}
$m prf n$ is $m$ minus $n$ if $mgeq n$ and otherwise $0$.
end{document}

documentclass{article}
usepackage{mathabx}
begin{document}
$xdotdiv y$
end{document}