Onkarah is a variation of Omkara(h) in Sanskrit. It meas the word/syllable
Om or aum which has vast significance in Eastern thought. In Punjabi onkara means one, as in one God. Having an interest in both Sikhism, hence the Punjabi, and in Vedanta philosophy, hence the Sanskrit, I opted for the less common spelling to come closer to the Punjabi in the Sikh Mool Mantra whilst keeping a foot in Vedanta and Sanskrit.
The Sikh Mul Mantra is said to summarise the Sikh religion in a short sentance (from
wikipedia link):
English: One Universal Creator, the Name is Truth, Creative Being (personified), Without fear, Without hatred, timeless Image, beyond birth, Self-existent, by the Guru's Grace.
Punjabi: ੴ ਸਤਿ ਨਾਮੁ ਕਰਤਾ ਪੁਰਖੁ ਨਿਰਭਉ ਨਿਰਵੈਰੁ ਅਕਾਲ ਮੂਰਤਿ ਅਜੂਨੀ ਸੈਭੰ ਗੁਰ ਪ੍ਰਸਾਦਿ ॥
ISO 15919 transliteration:
Ika ōaṅkāra sati nāmu karatā purakhu nirabha'u niravairu akāla mūrati ajūnī saibhaṃ gura prasādi Simplified transliteration: Ik ōaṅkār sat nām kartā purkh nirbha'u nirvair akāl mūrat ajūnī saibhaṃ gur prasād ||
A chilled song version on you tube here:
http://www.youtube.com/watch?v=f3zUYK4YU8M