text over equal latex
documentclass[preview]{standalone}
usepackage[utf8]{inputenc}
usepackage{amsmath}
newcommand{approxtext}[1]{ensuremath{stackrel{text{#1}}{approx}}}
begin{document}
$displaystyle
A stackrel{text{text}}{approx} B
$,
$displaystyle
A approxtext{test} B
$
end{document}