gatsun
A forceful, hard impact — hitting your head on something, being struck by a blunt object, or a shocking verbal blow. Conveys sudden, painful force.
💡Bumping your head on a low beam — 'I hit my head gatsun on the beam.'
頭をがつんとぶつけた。
I bumped my head gatsun.
He ___ hit his head on the low doorframe.
低いドア枠に頭を○○とぶつけた。