The Greek verb akyroo means to nullify, cancel, or make invalid — to render something without authority or binding force. Formed from the alpha-privative and kyrios (lord, authority), it means literally 'to de-lord' — to strip something of its authoritative validity. It appears in Matthew 15:6 and Galatians 3:17 in theologically charged contexts.
Jesus uses akyroo in Matthew 15:6 to charge the Pharisees with having 'made void the word of God for the sake of your tradition.' Their elaborate system of oral tradition, rather than protecting God's law, had actually nullified it — stripped it of its authoritative demand. This is one of Jesus' sharpest critiques of religious legalism: human tradition can become the enemy of divine command. Paul uses the same verb in Galatians 3:17 to argue the reverse: the Mosaic law, coming 430 years after Abraham's covenant, cannot akyroo (nullify, cancel) the prior covenant promise. The promise of grace in Abraham is inviolable; the law does not cancel it. Both uses of akyroo circle around the question of what holds ultimate authority: God's word and promise, or human systems and additions.