Historical Rules · 7 August 2020
Rule 701.3d
Official source text from the 7 August 2020 Rules release
To “unattach” an Equipment from a creature means to move it away from that creature so the Equipment is on the battlefield but is not equipping anything. It should no longer be physically touching any creature. If an Aura, Equipment, or Fortification that was attached to an object or player ceases to be attached to it, that counts as “becoming unattached [from that object or player]”; this includes if that Aura, Equipment, or Fortification leaves the battlefield, the object leaves the zone it was in, or that player leaves the game.