Flash a smile - Idioms by The Free Dictionary
flash a smile
flash (someone) a smile
To smile at someone, usually quickly and unexpectedly. She was sad this morning, but I think she's feeling better now—she flashed me a smile before she left.
flash a smile (at someone)
Fig. to smile quickly and perhaps briefly at someone. She flashed a smile at me as if she recognized me.
References in periodicals archive
Pretend you just noticed him right before you reach him, then catch his gaze and flash a smile
as you pass.
Everyday, Stella by Starlight, as she was called even though she worked days, would walk a few blocks to work and flash a smile
that melted your heart.