Entry
  1. Adverb (fukushi), Adverb taking the 'to' particle

    with a collapse; with a slump

    Onomatopoeic or mimetic word

    車で後ろから追突された時首がガクッとなりました。
    My neck snapped when my car was hit from behind.

Also written がくっカクンかくんカクンッカクンっかくんっ

Pitch on OJAD