A percolator, also simply known as a \’perc,\’ is a special glass design that increases water filtration inside of a bong, bubbler, or other water pipes by adding an additional chamber for the smoke to be filtered through. There are many different types of percolator common, but they all serve to improve the water filtration process so your cannabis bong hit is as smooth as possible.
Merriam-Webster Online Dictionary
percolator (noun)one that - percolates , specifically a coffeepot in which boiling water rising through a tube is repeatedly deflected downward through a perforated basket containing ground coffee beans to extract their essence
Diffuser, Filter, Bubbler, Recycler, Perc