The phrase "dozen upon dozens" means a large number of something, many times over. It suggests there are numerous groups of twelve items or people. Full definition
One of the most common traps seen in technical resumes is an abundance of technical jargon, including space - eating lists of dozens upon dozens of technical skills. (resume-now.com)
With dozens upon dozens of courses, various mini games, a level editor and two downloadable expansions, Trials HD has a lot of game for the price. (xblafans.com)
While there are literally dozens upon dozens of best practices, three of them would catch most faculty eyes. (educationworld.com)