adverb taking the 'to' particle, adverb
with a thud; heavily; plumply
Mimetic word for a heavy, dull impact or a plump, weighty appearance. Often used with と.
大きな荷物がドシンと落ちた。
The heavy luggage fell with a thud.
彼はドシンとソファに座った。
He sat down heavily on the sofa.