What in math is a Cumulative Review?

Answer 1

It means you'll be reviewing (and you'll probably be tested on) everything you've gone over in class thus far. This happens in most classes. The teacher just wants to know if you've retained all the information you were supposed to've learned by now.

Answer 2

It's not strictly a Math thing. It's just a review (test, quiz or other format) of what you've learned up to a certain point, usually determined by a teacher.