A downward slap in the face to someone who has done you wrong, lied, or in any means made your life complicated. Unlike it's counter parts AKA the bitch slap, and pimp slap which is only inteneded to humiliate, and gain currency
Some one is spreading rumors about you at work. Thus creating alot of tension from co-workers, so you would confront that person and give them the justice hand. Smacking them down to the floor so they look up at you and realize to respect.