こつん

adverb taking the 'to' particle, noun

with a light knock; with a tap; with a bonk

Mimetic word for a light, crisp knocking or tapping sound, often of a small hard object hitting something. Used adverbially with と.

• 誰だれかがドアをこつんとノックした。

  Someone gave a light knock on the door.

• 彼かれは机つくえをこつんと指ゆびで叩たたいた。