Grounding, in Wicca and other occult traditions, is a ritual act of connect the body to the earth, Mother Earth or Goddess. This is a Witchcraft practice since it is believed the earth represents the body of the Goddess. Through practicing grounding the person draws natural forces of the Goddess into him/herself. The reverse also can be affected; negative energy within the person can be transferred into the earth.
A similar effect is seen within Christianity when a person claims to be rooted in Christ, relying on Christ for guidance and strength. The difference is Witchcraft and occult are nature based religion and practices whereas Christianity is theological. A.G.H
Drury, Nevil. The Watkins Dictionary of Magic. London. Watkins Publishing. 2005. p. 121