The phrase "second cohort" refers to a group of people or things that are part of the second set or category, following a previous group. Full definition
Second cohort of schools selected to receive on - site support from Middle School Matters Institute (meadowscenter.org)
He notes that Clayton Dubilier & Rice, the private equity firm where he serves as a senior advisor, is now funding 20 students in his MBA program, with a second cohort to start in January. (fortune.com)
A second cohort is working its way through the program, with a third set to start this fall. (canadianbusiness.com)