adverb, adverb taking the 'to' particle, noun or participle which takes 'suru'
Onomatopoeia for the sound of a liquid bubbling or gurgling, often in a small container or when poured.
やかんのお湯がコポコポと沸いている。
The water in the kettle is bubbling away.
瓶から酒をコポコポと注いだ。
I poured sake from the bottle with a glug-glug sound.