Mudangchum(무당춤) means a traditional Korean shaman dance. Literally, it is danced by one or more Mudangs or traditional Korean shamans often in a trance state.
There are many varieties, but the dance shown in this video is the one variety originating from the Dodanggut exorcism ritual of Gyeonggido Province.
Source: KBS1 국악 한마당 has all the rights.