Keyword cannibalization
Keyword cannibalization is two or more pages on the same site competing for the same search query, splitting the signal so both rank worse than one page would. The fix is one clear target per page, enforced with an intent map.
It usually happens by accident: a homepage and an about page both optimized for the head term, or three blog posts circling the same question. Google then has to pick between your own pages, and often ranks the wrong one, or ranks each inconsistently, query by query.
You diagnose it in Search Console by reading queries against pages: when one query shows impressions across multiple URLs with mediocre positions on each, the pages are splitting a signal one of them should own.
We write from experience here: we found our own about page competing with our homepage across six queries and losing all of them. De-optimizing the about page, giving it a brand job instead of a keyword job, is what an intent map exists to prevent from the start.