Aum, or Om, is merely a sound, as well as the universal mantra. According to ancient sanskrit, the sound creates a vibration that resonates at a frequency throughout the world. The purpose is well stated in the Upanishads: “What world does he who meditates on Aum until the end of his life, win by That? If he meditates on the Supreme Being with the syllable Aum, he becomes one with the Light, he is led to the world of Brahman [the Absolute Being] Who is higher than the highest life, That Which is tranquil, unaging, immortal, fearless, and supreme.” – Prashna Upanishad 5:1,5,7

We are not immortal Holly, life is precious and symbols are brainwash. Get a butterfly instead! Nature is beautiful to God not symbols or words. From Holly

In Hinduism, Om is the sound of the universe. It is harmony and the ultimate peace. It represents the rejoining of the immortal soul with the rest of the universe. Just because you think it looks cool is a pretty superficial reason to get a tattoo - it will be PERMANENT. Plus, it's not even that unique a tattoo. It has become very mainstream now.

If you don't know what it means, you shouldn't get a tattoo of it.

"In Hinduism The syllable Aum is first described as all-encompassing mystical entity in the Upanishads. Today, in all Hindu art and all over India and Nepal, 'Aum' can be seen virtually everywhere, a common sign for Hinduism and its philosophy and theology." "The syllable is mentioned in all the Upanishads, specially elaborated upon in the Taittiriya, Chandogya and Mandukya Upanishad set forth as the object of profound religious meditation, the highest spiritual efficacy being attributed not only to the whole word but also to the three sounds a (a-kāra), u (u-kāra), m (ma-kāra), of which it consists. A-kara means form or shape like earth, trees, or any other object. U-kara means formless or shapeless like water, air or fire. Ma-kara means neither shape nor shapeless (but still exists) like the dark matter in the Universe. When we combine all three syllables we get AUM which is a combination of A-kara,U-kara, andMa-kara." "The Bhagavad Gita (8.13) has: Uttering the monosyllable Aum, the eternal world of Brahman, One who departs leaving the body (at death), he attains the superior goal. The Bhagavad Gita (9.17)has: Krsna says to Arjuna - "I am the father of this universe, the mother, the support and the grandsire. I am the object of knowledge, the purifier and the syllable Oḿ. I am also the Ṛg, the Sāma and the Yajur Vedas." " "In Puranic Hinduism, Aum is the mystic name for the Hindu Trimurti, and represents the union of the three gods, viz. a for Brahma, u for Vishnu and m for Mahadev which is another name of Shiva. The three sounds also symbolize the three Vedas (Rigveda, Samaveda, Yajurveda). According to Hindu philosophy (see Mandukya Upanishad), the letter A represents creation, when all existence issued forth from Brahma's golden nucleus; the letter U refers to Vishnu the God of the middle who preserves this world by balancing Brahma on a lotus above himself, and the letter M symbolizes the final part of the cycle of existence, when Vishnu falls asleep and Shiva has to breathe in so that all existing things have to disintegrate and are reduced to their essence to him. More broadly, Aum is said to be the primordial sound that was present at the creation of the universe. It is said to be the original sound that contains all other sounds, all words, all languages and all mantras." Source and further information: http://en.wikipedia.org/wiki/Aum

Aum (also Om or, more rarely, Ohm; Sanskrit: ॐ) is a mystical or sacred syllable in the Hindu, Jain, and Buddhist religions. It is placed at the beginning of most Hindu texts as a sacred exclamation to be uttered at the beginning and end of a reading of the Vedas or previously to any prayer or mantra and also is said in the beginning of any puja (religious ritual). The Mandukya Upanishad is entirely devoted to the explanation of the syllable. http://en.wikipedia.org/wiki/Aum

Everything

As far as I understand, it's pretty much everything and nothing. The universe, and nothing at all.

Think it's " No" misspelled

its the chant you do - durng YOGA.