An Everythingship is a relationship but more. When you are in an Everythingship you are not just their boyfriend/girlfriend, you are their Bestfriend, soul mate, and their boy/girl friend. It takes two people who truly love each other to have an Everythingship.
A feeling of knowing that the person you are with is perfect for you in the best and worst way possible. Instead of being in a relationship or a friendship you are in an 'everythingship'