EntryCommonJLPT N3
  1. Adverb (fukushi), Adverb taking the 'to' particle

    soundly (sleeping); fast (asleep)

    Onomatopoeic or mimetic word

    昨夜はぐっすり眠れなかった。
    I couldn't sleep well last night.

Also written グッスリ

Pitch on OJAD