Hi
Could you please tell me how common this idiom (flash on) is among native speakers? The Oxford dictionary says that it is informal, and that means it should be fairly common. I asked a native speaker friend from the USA recently and she said she had never heard this idiom in her entire life.
Flash on: to suddenly realize something. It flashed on me that she had been lying on the while.
https://www.oxfordlearnersdictionaries.com/definition/american_english/flash-on
Thanks,
Tom
I know what it means, but I never say it and I can't remember ever hearing it.
flash on, Slang.- to have a sudden thought, insight, or inspiration about.
- to have a sudden, vivid memory or mental picture of: I just flashed on that day we spent at the lake.
- to feel an instantaneous understanding and appreciation of.
https://www.dictionary.com/browse/flash -on
Clive
Mr. TomIt flashed on me that she had been lying on the while.
I prefer to lie on a couch or on a bed. 
Mr. Tom It flashed on me that
< blank look on my face >
I don't think you'll find many instances of 'flash on' with this meaning in the usual corpora. Practically all examples you find are about lights that flash on and off.
CJ
Me too..
These are used.
It came to me in a flash...
In a flash of inspiration,....