Verb
To learn (something) more than is necessary; to study excessively, to take (something) too much to heart.
(psychology, education) To learn (something) to the point where responses become instinctive.
(modeling) Mostly when talking about neural networks, to learn a task to the point where responses actually start to degrade. Compare with overfit, in model tuning contexts.
Source: en.wiktionary.org