Kundalini (kuṇḍalinī, Sanskrit: कुण्डलिनी) literally means coiled. In yoga, a “corporeal energy” – an unconscious, instinctive or libidinal force or Shakti, lies coiled at the base of the spine. It is envisioned either as a goddess or else as a sleeping serpent, hence a number of English renderings of the term such as ‘serpent power’. The kundalini resides in the sacrum bone in three and a half coils and has been described as a residual power of pure desire.
Definition courtesy Wikipedia.