Four line equality

Here is a command, \superequiv that seems to be what you want:

\documentclass{article}

\newcommand\superequiv{\mathrel{\rlap{\raisebox{\fontdimen22\textfont2}{$=$}}\raisebox{-0.5\fontdimen22\textfont2}{$ = $}}}

\begin{document}

    \[ A \superequiv B \]%

\end{document} 

The symbol is classified in Unicode as U+2263 STRICTLY EQUIVALENT TO. The only math font providing it is, as far as I know, STIX.

\documentclass{article}

\usepackage{stix}

\begin{document}

\[{=\equiv\Equiv}\quad A \Equiv B_{\Equiv_{\Equiv}} \]

\end{document}

With other math fonts you have to emulate it. Using the same idea as Bernard, here is a possibility with Computer Modern

\documentclass{article}

\makeatletter
\DeclareRobustCommand\Equiv{\mathrel{%
  \mathchoice
    {\Equiv@\textfont\displaystyle{.45}}
    {\Equiv@\textfont\textstyle{.45}}
    {\Equiv@\scriptfont\scriptstyle{.5}}
    {\Equiv@\scriptscriptfont\scriptscriptstyle{.55}}
}}
\newcommand{\Equiv@}[3]{%
  \rlap{\raisebox{#3\fontdimen5#12}{$\m@th#2 = $}}%
  \raisebox{-#3\fontdimen5#12}{$\m@th#2 = $}%
}
\makeatother

\begin{document}

\[{=\equiv\Equiv}\quad A \Equiv B_{\Equiv_{\Equiv}} \]

\end{document}

I'm afraid that, with other fonts, you have to tailor the parameter (the third argument to \Equiv@ in the code above).

The symbol is \Equiv in unicode-math, and all or nearly all OpenType math fonts include it.

In PDFTeX, the \Equiv symbol is in the stix and stix2 packages.