What, where, who, why, etc. the devil… Definition 1 of 3Pro Tip 1/3Surprise Factor Expresses shock or unexpectedness of a situation or action. What the devil! You scared me! Pro Tip 2/3Annoyance Emphasis Highlights irritation or frustration with someone or something. Where the devil are my keys? Pro Tip 3/3Disbelief Tone Used when something is hard to believe or accept. How the devil did you solve that?