When a yukkuri with braids, typically either a reimu or marisa, or in some cases a meling or sakuya is moving them up and down or side to side quickly, typically when in a state of happiness or terror. Distinct from the braids tag due to flapping being an involuntary action.
It might have been "mister_braids" except there's only one picture tagged for that (unless there were more from the infamous tagging holocaust of the old OYP).
And why isn't "flapping" "flap_flap" in consistency with yukkuri speech patterns?
starshine said: And why isn't "flapping" "flap_flap" in consistency with yukkuri speech patterns?
I'm starting to wonder whether you're actually joking. Regular words is easier to search, exception being rub_rub and lick_lick because we've been using them forever.