What is "man-in-the-middle"

Usage examples of "man-in-the-middle".

And because he's still basically a little kid, and not fully in control of his own metaprogramming, instead of adjusting his outlook so that he isn't bored anymore, he sneaks out through his bedroom gate (which big-Manni-ghost reprogrammed for him sometime ago so that it would forward to an underused public A-gate that he'd run a man-in-the-middle hack on, so he could use it as a proxy teleport server) then down to the underside of Red Plaza, where skinless things gibber and howl at their tormentors, broken angels are crucified on the pillars that hold up the sky, and gangs of semiferal children act out their psychotic fantasies on mouthless android replicas of parents and authorities.