A rediculous way to say "Oh My God". Capitalisazation doesn't matter, and usually has an exclamation mark after it. Who knows where this "word" originated from but time to time you may hear people use it.
Person 1: I totally just asked this guy out and he actually said yes!
Person 2: Aw, you are soo lucky, like, ewmahgawd!
Aw-Mai-Gawd is another term for: Oh My Gawd (God)
It is used by complete noobs, but is very annoying.
All you do is put it in one word and make 'Ai' sound for My or Mai.
Easy enough eh?