Apekdyomai means to strip off completely, divest entirely, or discard. The intensive prefix apo combined with ekdyō (to strip) indicates total, decisive removal. Paul uses it metaphorically for the stripping away of the sinful nature at conversion (Colossians 2:11) and for Christ's complete triumph over demonic powers at the cross.
Colossians 2:15 is one of the most triumphant images of the cross in the New Testament: Christ "stripped off" the powers and authorities and displayed them publicly, triumphing over them. The same verb used for total divestiture of clothing pictures the complete de-arming of Satan's kingdom at Calvary. The cross was not defeat — it was the greatest cosmic victory in history.