Flabbergasted/ˈflæbərɡæstɪd/ Definition 1 of 1Pro Tip 1/3Emotional Intensity Used to express a strong emotional reaction, often shock or disbelief. She was flabbergasted by the surprise party. Pro Tip 2/3Informal Use Suitable for casual conversation, but not for very formal writing or speaking. When he won the lottery, he was absolutely flabbergasted. Pro Tip 3/3Unexpected Situations Often used when an event is so surprising, it's almost hard to believe. The audience was flabbergasted by the magician's trick.