The Ouroboros [or-oh-bohr-ohs] is an ancient symbol depicting a serpent or dragon eating its own tail, which often represents self-reflexivity or cyclicality, especially in the sense of something constantly re-creating itself, the eternal return, and other things perceived as cycles that begin anew as soon as they end (compare with phoenix). It can also represent the idea of primordial unity related to something existing in or persisting before any beginning with such force or qualities it cannot be extinguished.
The ouroboros has been important in religious and mythological symbolism, but has also been frequently used in alchemical illustrations, where it symbolizes the circular nature of the alchemist’s opus. It is also often associated with Gnosticism, and Hermeticism. The earliest known representation of the Ouroboros is contained in the Egyptian Book of the Netherworld. The self-begetting sun god Atum is said to have ascended from chaos-waters with the appearance of a snake, the animal renewing itself every morning, and the deceased wishes to turn into the shape of the snake Sato (‘son of the earth’), the embodiment of Atum.
The Daily Omnivore 