Leech/liːtʃ/ Definition 1 of 5Pro Tip 1/3Natural Habitats Leeches are common in wet environments like swamps, so context implies seeking them there. Wearing boots helps prevent leeches in the jungle. Pro Tip 2/3Physical Sensation Usually, you don't feel a leech right away because they release anesthetics. I didn't notice the leech until I saw blood. Pro Tip 3/3Medicinal Use Leeches can be used in therapy, which isn't negative like the parasitic connotation. The doctor applied medicinal leeches post-surgery.