It's a Midwest thing. When someone cuts in front of you rudely, when you are surprised, when you bump into someone, or when something is offensively funny, you use the word ope.
(noun) -An interjection of surprise after an unexpected event occured. It can be for either bad or good connotation depending on the situation.
You and a friend are fighting over an ice creamcone and it slips out of your hands and lands on your dogs head, so you and your friend look at each other and say, "Ope!"