ガクンガクン

adverb taking the 'to' particle, adverb

jerkingly; with a series of jolts

Describes repeated, sharp, jerky movements, often of a vehicle or body part. Mimetic adverb typically used with と or as an adverbial modifier.

• バスがガクンガクンと揺ゆれた。

  The bus jerked along with a series of jolts.

• 彼かれはガクンガクンと首くびを振ふった。

  He shook his head in a jerky, repeated motion.