Meaning "Oh My God". This is the way in which those girls who talk really fast say it. when spoken correctly the three words should become one, "Ohmygoyy".. with the "Goyy" sound being held within the throat and whilst the tongue is suspended slightly. It's very important that you say it in this exact way, otherwise you might come across as Working Class.
"Oh My Goyy, that's like so un-frickin real!"