Sexual play which is an extreme form of BDSM, generally the two partners agree to not set a 'safety word' and gives total power to the dominant over the submissive. Results can include minor/major permanent injuries, or death if not practiced correctly.
Many forms of this are around, breathplay (erotic asphyxiation), knifeplay (playing with knives), gunplay (guns), blood/cutting play (deliberate cuts to draw blood).
Not often seen and praticed but generally most people who pratice this, do so in a consensual way.
Did you hear? Jim died while while him and his spouse were praticing edgeplay.