adverb taking the 'to' particle, adverb
with a flash; brightly; dazzlingly
Onomatopoeic adverb describing a single, brief flash or sparkle of light. Often used with と (ぴかりと). Compare ピカッと for a sharper, more abrupt flash.
See also: ピカッと
星がぴかりと光った。
A star twinkled brightly.
カメラのフラッシュがぴかりと光った。
The camera flash went off with a flash.
キラリ is also an onomatopoeic adverb for a brief sparkle, but often implies a more delicate or gem-like glitter compared to ぴかり's broader flash.
Onomatopoeic word mimicking a brief flash or sparkle of light. The exact origin is uncertain, but it is related to the mimetic root ピカ (pika), which represents light or brilliance.