Merriam Webster
noun. ho·me·op·a·thy \ˌhō-mē-ˈä-pə-thē
 A system of medical practice that treats a disease especially by the administration of minute doses of a remedy that would in larger amounts produce in healthy persons symptoms similar to those of the disease.

Urban Dictionary
An alternative, none science-based medicine which originated on the now outdated and completely disproved principle that water holds a “memory” of diluted substances, and that “the similar cures the similar”. That is, even if they are diluted to a level where absolutely no molecules of the said substance can remain. Various studies have repeatedly shown that homeopathic remedies are as effective as any placebo treatments.