adverb taking the 'to' particle, adverb
with a heavy thud; plopping down heavily
Mimetic word describing something heavy falling or landing with a dull, solid sound, or a person sitting down heavily and unceremoniously.
疲れたので、ソファにどかりと座った。
Exhausted, I plopped down heavily onto the sofa.
大きな石がどかりと落ちてきた。
A large rock came down with a heavy thud.