To (hypothetically) show enormous anger, disfavor, or regret for someone's actions or something that happens after one has died. That is, if someone were still alive, they would be greatly upset, angered, or disgusted by what has happened. I can't believe you're using our employees' pension payments to prop up a Ponzi scheme. The founder of this once-great company would be turning in his grave to see its directors stoop so low. Your poor mother would turn over in her grave if she heard the horrible things you were saying about your sister. I can't believe you wrecked your grandfather's prized truck. That's enough to make him turn over in his grave!