The phrase "wafer crumbs" refers to tiny pieces or crumbs that are left behind when a wafer, which is a thin and crispy biscuit-like snack, is eaten or broken apart. Full definition
Airy and creamy cheesecake made with pureed raspberries, marshmallow creme and non-dairy whipped topping in vanilla wafer crumbs crust. (easydessert.org)
When I have made other press in the pan pie crusts in the past (think graham cracker or vanilla wafer crumb crusts) I use a glass that has straight sides on it to press the mixture into the pan and it works wonderfully, produces a nice even top to the crust as well as even sides. (oatmealwithafork.com)