To say that you know nothing about something, or that you have no responsibility for or connection with something. (Cambridge Dictionary)
To deny responsibility for: Repudiate. (Merriam – Webster)
If you disavow something, you say that you are not connected with it or responsible for it. (Collins Dictionary)
Deny any responsibility or support for. (Oxford Dictionaries)
What is Google’s Disavow Tool & How to Use it? – A step-by-step Guide.