Any of various chiefly aquatic bloodsucking or carnivorous annelid worms of the class Hirudinea, of which one species(Hirudo medicinalis) was formerly used by physicians to bleed patients.

• 水蛭，蚂蟥，欧洲医蛭蛭纲环节幼物中几种主要水生吸血或食肉环节蠕虫中的一种，其中的（欧洲医蛭）过去曾被医生用于为病人放血