Onomatopoeia for munching or crunching — the crisp sound/behavior of biting into something hard (e.g., a cracker).
彼は会議中にポリポリとせんべいを食べていた。
He was crunching on crackers during the meeting.
リンゴをポリポリかじる音が台所から聞こえた。
I heard the sound of someone munching an apple in the kitchen.
小腹が空いたのでポリポリとナッツをつまんだ。
I was a bit hungry so I nibbled on some nuts.
Onomatopoeia for lightly scratching an itch — the sound or action of scratching gently.
蚊に刺されたところをポリポリとかいてしまった。
I ended up scratching where I was bitten by a mosquito.
先生は後ろでポリポリと頭をかいていた。
The teacher was lightly scratching his head in the back.
乾燥で肌がかゆく、夜中にポリポリかいて目が覚めた。
My skin was itchy from dryness and I woke up scratching at night.