(Onomatopoeia) with a quick big bite or mouth opening — describes snapping something into the mouth or opening the mouth widely to take a bite; mimetic of a quick, decisive mouth action.
子どもがりんごをぱくっとかじった。
The child took a big bite of the apple.
猫が餌を見てぱくっと飛びついた。
The cat lunged and snapped the food into its mouth.
驚いて彼は口をぱくっと開けた。
Startled, he opened his mouth wide.