According to Hindu Philosophy , Brahma (the creator) first manifested himself as name and then as a form i.e universe. This universe was the result of his expression but behind which stands an inexpressible Sphota.
Sphota is the material of all words. In other words the idea which generates in mind takes the form of a particular word. However, the idea itself has no language so one can say a Sphota is a matter which forms the basic building block of ideas.
This is the Sphota through which lord created this universe. The Sphota has one word as its only possible symbol, and that is Om and by no means the word can be separated from the idea. The Om is the eternal word through which all this universe has been created.
Scientifically speaking Om is pronounced as (A.U.M). All articulate sounds are produced in the space are through the root of our tongue and ending in the lips - the throat sound is A and lips sound is M. U represents the rolling forward of the impulse which begins at the root, flows through the tongue and ends in the lips. If properly pronounced, this Om represents the whole phenomena of sound generation.
Om is therefore the fittest symbol of Sphota, which is the real meaning of OM.