Other forms: eaten away; eating away; eats away; ate away
To eat away is to gradually wear away or destroy, the way salt water will slowly eat away at the wooden pilings holding up a dock.
Sharply carved granite along a rocky shore is evidence that the sea will eat away at anything that spends enough time with waves crashing on it. In addition to corrosive substances like salt water and acid, an emotion like regret or anger can figuratively eat away too: "I'm done being mad at my brother. That negative emotion never bothers him, but it eats away at me."