The abbreviation OMR means OH MY RUKI and for the fans of the GazettE has the same meaning as OH MY GOD.
Word is commonly used in online or web chat when a person does not have time to print out the entire word OH MY RUKI.
When you want to exclaim that something is fantastic and gorgeous.
When you want to express that you are surprised with something nice or beautiful.
Person 1. : OMR have You seen the GazettE new look?
Person 2. : Yup. OMR they look really GORGEOUS n BRILLIANT.