1The repeated opening and closing of the mouth (e.g., gasping, or mouth movements while talking or surprised).
赤ちゃんが嬉しくてぱくぱく口を動かしている。
The baby is happily opening and closing his mouth.
彼は驚いて口をぱくぱくさせたが、何も言えなかった。
He opened and closed his mouth in surprise but couldn't say anything.
魚が水面でぱくぱくしているのを見た。
I saw a fish at the water's surface opening and closing its mouth.
2Describes flapping or gaping open-and-shut motions (e.g., a sole flapping, something gaping and closing).
古い靴の底が歩くたびにぱくぱくする。
The sole of the old shoe flaps with every step.
箱のふたが劣化して、開け閉めするとぱくぱく鳴るようになった。
The box lid has deteriorated so it makes a flapping noise when opened and closed.
3Eating heartily or voraciously; gobbling or munching enthusiastically.
子どもたちは給食をぱくぱく食べてあっという間に完食した。
The children ate their school lunch heartily and finished in no time.
お腹が空いていたので、彼はぱくぱくと何皿も食べた。
He was so hungry that he gobbled down several plates.
おいしそうにスープをぱくぱく飲む猫の動画を見た。
I watched a video of a cat happily slurping its soup.
ダイエット中なのに彼はぱくぱく食べている。
Even though he's on a diet, he's eating heartily.