ボコッ

adverb taking the 'to' particle

with a thwack; with a thump

Mimetic word for a dull, hollow impact sound, like hitting something soft or hollow.

• ボールが壁かべにボコッと当あたった。

  The ball hit the wall with a thump.

adverb taking the 'to' particle

conspicuously; noticeably; gaping

Describes a hole, bulge, or dent that is clearly visible or prominent. Often used with 穴, へこみ, ふくらみ.

• 壁かべにボコッと穴あなが開あいている。

  There is a conspicuous hole in the wall.