Jakob Nielsen's 10 general principles for user interface design. They are called "heuristics" because they are more in the nature of rules of thumb than specific usability guidelines.
As an adjective, heuristic means "pertaining to or aimed at discovery or steering your attention in a fruitful direction, as opposed to making an evaluation or final judgement."
O. Kashefi, and R. Hwa. Proceedings of the Sixth Workshop on Noisy User-generated Text (W-NUT 2020), page 200--208. Online, Association for Computational Linguistics, (November 2020)