It refers to the player seated two positions to the right of the dealer button, just before the cut-off position. It's typically one of the later positions at the table in a full-handed game.
Being in the hi-jack position grants a player a more advantageous position than players in earlier positions, allowing for more information about opponents' actions before making decisions. However, it's not as advantageous as the later positions like the cut-off or the button, as there are still several players left to act after the hi-jack.