A magical parasite that lives in the fur or feathers of some magical creatures, and can also infest magical items. Chizpurfles are 1/20″ long and are crab-like in appearance (FB).
In wizard dwellings, they attack magical objects, and eat lingering drops of potions left in cauldrons. In muggle homes, they attack electrical objects, causing them to not work properly (FB). There are potions that can get rid of them, but severe infestations require a visit from the Pest sub-division of the Department for Regulation and Control of Magical Creatures (FB).
"Chizpurfle" is a multiple choice answer on the Grade 1 WOMBAT test, on JK Rowling's original website (JKR).
"chizz" Eng. cheat, swindle + "purfle" Eng. a fur trimming or embroidered border of a garment (NSOED)
Their size (1/20 inch), and the fact that they infest the fur of magical creatures, reminds one of muggle fleas.