ゴッチン

adverb, adverb taking the 'to' particle, noun or participle which takes 'suru'

with a bump; with a clonk; with a clank

Onomatopoeia for a solid impact sound, especially a head hitting something. Often used with と or as a する verb.

• 転ころんで頭あたまをゴッチンとぶつけた。

  I fell and bumped my head with a clonk.