If you reject something or disown it, you can call this renunciation. Sorry, your renunciation of your membership in the American Association of Retired People will not make you any younger.
Use the noun renunciation especially when you mean you have given up your religious or political beliefs or some cause you previously supported. When you drop a political party to become an independent, you mean it to be a renunciation of all the infighting, backstabbing, and finger pointing that have become “politics as usual.”
the act of renouncing; sacrificing or giving up or surrendering (a possession or right or title or privilege etc.)
an act (spoken or written) declaring that something is surrendered or disowned
rejecting or disowning or disclaiming as invalid
the state of having rejected your religious beliefs or your political party or a cause (often in favor of opposing beliefs or causes)