From Longman Dictionary of Contemporary Englishfall flat on your/something's facefall flat on your/something's facea) FALLto fall so that you are lying on your chest on the ground Babe slipped and fell flat on her face. b) informalFAIL to not have the result you want or expect, especially when this is embarrassing The theory falls flat on its face when put into practice. → flat
Examples from the Corpus
fall flat on your/something's face• As we were going out to the car Babe slipped and fell flat on her face.• At last, after several near misses, I fall flat on my face.• Because if you don't a fresh ambition or optimistic plan will fall flat on its face.• It is also a nation waiting for her to fall flat on her face.• Writers strive for a universal experience distilled from personal memories and tend to fall flat on their faces.• But once the ball tips, the game falls flat on its face faster than a top-ranked team after a first-round upset.• She fell flat on her face getting out of the car.• The last time I wore high-heeled shoes I fell flat on my face outside a restaurant.• Yet there are certain composers who fall flat on their face unless the adrenalin really start to flow. 