Have you ever bought a bookshelf?
Well, that’s upzoning.
Upzoning refers, basically, to liberalizing the zoning code on a piece of land to allow more intense development (larger, taller, denser, etc.) This is obviously sometimes controversial, as in the case of allowing denser development in single-family zones. Sometimes it’s pretty uncontroversial, such as permitting skyscrapers in Manhattan. (Although, believe it or not, Manhattan also has its NIMBYs.)