To deliberately get rid of something you already learned, because it is now in your way. This is not forgetting — forgetting happens to you, unlearning is work you choose to do. And it is not learning the opposite either; it is the harder job of loosening a habit that has become automatic so that a new one has room to form.

The word is nearly always about habits, beliefs, and skills rather than facts. A tennis player has to unlearn a bad serve. A driver moving from Taiwan to Britain has to unlearn keeping right. A student who spent six years translating every English sentence from Chinese in their head has to unlearn that before they can speak at normal speed. Notice the shape of all of these: what you are undoing was once useful, or at least once worked. That is exactly why it is so hard to drop.

It also carries a social and political sense, common now in writing about race, gender, and culture: 'unlearning the assumptions we grew up with'. Here it means examining something you were taught so early that it never looked like a lesson, and choosing to put it down.

Grammar: it is a normal verb — unlearn, unlearned, unlearning. Both 'unlearned' and 'unlearnt' exist as the past form, with 'unlearnt' more British. Be careful, though: the adjective 'unlearned' (often said un-LERN-id, three syllables) is a separate old word meaning 'having no education', and it is not the past tense of this verb.

There is a famous line often quoted about it — that the illiterate of the future will be those who cannot learn, unlearn, and relearn. That trio, 'learn, unlearn, relearn', is how you will most often see the word in the wild.