Keyword cannibalization in this context means your paid ads and your free organic search results are competing for the same keywords at the same time. This can be a waste because you are paying for clicks you might have gotten for free. One way to handle it is to check which keywords you already rank for organically, then pull those out of your paid campaigns or reduce how much you bid on them. You can then use your paid budget on keywords where your organic ranking is weak. This way, both channels support each other instead of fighting. Have you ever noticed your ads and organic results competing for the same searches?