The tendency of an examinee scoring above or below the mean of a distribution on a pretest to score closer to the mean on the post-test.
Yarbrough, D. B., Shulha, L. M., Hopson, R. K., and Caruthers, F. A. (2011). The program evaluation standards: A guide for evaluators and evaluation users (3rd ed.). Thousand Oaks, CA: Sage.