This is the dictionary definition of this word:
a sudden brief burst of bright flame or light.
"the flare of the match lit up his face"
synonyms: blaze, flash, dazzle, burst, flicker
"the flare of the match"
a gradual widening, especially of a skirt or pants.
"as you knit, add a flare or curve a hem"
burn with a sudden intensity.
"the blaze across the water flared"
synonyms: blaze, flash, flare up, flame, burn; More
gradually become wider at one end.
"a flared skirt"
But in some examples I saw it used in a simular fashion to "flail"
In the example you gave I like to imagine it like how fire moves. its rapid random movements with a snap to them.
I hope this helps,