To express suprise. It is the combination of "Oh", "My" and "God" to form an incoherant word. Usually used online since saying it outloud does not hold the same meaning, because people cant tell you meshed the words together.
Spackerdave: Dude, i justf*cked your mom.
ReZ: ohmygawd
Pajama casual is a term used when working from home and preparing for a video conference. All business above the waist and your pajama pants down below.