With its threefold nature, special shape and unique sound, OM lends itself to a variety of detailed symbolic interpretations.
The symbol of AUM consists of three curves, one semicircle, and a dot.
The upper curve symbolizes the waking state (jagrat), in this state the consciousness is turned outwards through the gates of the senses. Because this is the first curve it signifies the most common ('majority') state of the human consciousness.
The lower curve signifies the dream state (swapna). In this state the consciousness of the individual is turned inwards, and the dreaming self beholds an enthralling view of the world behind the eye lids.
The middle curve signifies the state of deep sleep (sushupti) or the unconscious state. This is a state where the sleeper desires nothing nor beholds any dream.
These are the three states of an individual's consciousness, and since Indian mystic thought believes the entire manifested reality to spring from this consciousness, these three curves of the OM symbol therefore represent the entire physical phenomenon.
The dot signifies the fourth state of consciousness, known in Sanskrit as turya. In this state the consciousness looks neither outwards nor inwards, nor the two together. It signifies the coming to rest of all differentiated, relative existence. This utterly quiet, peaceful and blissful state is the ultimate aim of all spiritual activity. This absolute (non-relative) state illuminates the other three states.
Finally, the semi circle symbolizes maya (the non-real – the transitory state of consciousness) and separates the dot from the other three curves. Thus, it is the illusion of maya – the transitory state of consciousness that prevents us from the realization of this highest state of bliss.
The semi circle is open at the top, and when ideally drawn does not touch the dot. This means that this highest state is not affected by maya. Maya only affects the manifested phenomenon. This effect is that of preventing the seeker from reaching his ultimate goal, the realization of the One, all-pervading, unmanifest, Absolute principle. In this manner, the form of OM represents both the unmanifest and the manifest, the subtle and the physical realms of existence.
Over and above the threefold nature of OM as a sacred sound is the invisible fourth dimension which cannot be distinguished by our sense organs. The sense organs are restricted to material observations. This fourth state is the unutterable, soundless silence that follows the uttering of OM. A quieting down of all the differentiated manifestations, i.e. a peaceful-blissful and non-dual state. Indeed this is the state symbolised by the dot in the traditional iconography of AUM.