I always find it difficult to explain because I'd like to go into detail about it's meaning and where it comes from (to share) but I can't find any easy way of doing so; so, I usually just say "it's a buddhist prayer written in sanskrit" & most respond with "oh...ok, it looks cool".
Anyway, thought i'd give a little background on it for anyone who cares to learn.
It is pronounced: Om mani padme hum though there are various ways of saying it, depending on where you are from, etc. It is a mantra that is particularly associated with Avalokiteshvara (aka: Chenrezig, Kuan Yin, Guanyin.)
The mantra is especially revered by the devotees of the Dalai Lama, as he is said to be an incarnation of Chenrezig.
I've learned that it is quite difficult to really translate it into English and there are various ways of interpretation as the effect of the mantra lies beyond strict meaning.
Definition by H.H. the 14th Dalai Lama:
- "It is very good to recite the mantra Om mani padme hum, but while you are doing it, you should be thinking on its meaning, for the meaning of the six syllables is great and vast... The first, Om [...] symbolizes the practitioner's impure body, speech, and mind; it also symbolizes the pure exalted body, speech, and mind of a Buddha[...]"
- "The path is indicated by the next four syllables. Mani, meaning jewel, symbolizes the factors of method: (the) altruistic intention to become enlightened, compassion, and love.[...]"
- "The two syllables, padme, meaning lotus, symbolize wisdom[...]"
- "Purity must be achieved by an indivisible unity of method and wisdom, symbolized by the final syllable hum, which indicates indivisibility[...]"
- "Thus the six syllables, om mani padme hum, mean that in dependence on the practice of a path which is an indivisible union of method and wisdom, you can transform your impure body, speech, and mind into the pure exalted body, speech, and mind of a Buddha[...]"