In terms of astrology, mysticism and myth the spiral translates into meanings of spirituality and rebirth.In terms of spirituality, the spiral symbol represents the path leading from outer consciousness (materialism, external awareness, ego, outward perception) to the inner soul (enlightenment, unseen essence, nirvana, cosmic awareness).
In terms of rebirth or growth, the spiral symbol represents the consciousness of nature beginning from the core or center and thus expanding outwardly. This is the way of all things, as recognized by most mystics.
This is a painfully brief post on an infinitely expansive topic. For more information on spiral meaning and symbolism, visit this expanded page on the spiral symbol.