adverb
with a little roll; rolling once
Describes a small object rolling once, often into a hole or gap. Mimetic word.
ビー玉が床に落ちて、ころっと転がった。
The marble fell on the floor and rolled a little.
Used with verbs of change, forgetting, or falling, emphasizing that something happens in a quick, effortless, or complete manner. Often collocates with 忘れる, 変わる, 寝る, etc.
彼の名前をころっと忘れてしまった。
I completely forgot his name.
彼女は疲れて、ソファでころっと寝てしまった。
She was so tired that she suddenly fell asleep on the sofa.
adverb
disappointingly; let down
Expresses a sense of anticlimax or disappointment when something turns out to be less than expected. Often used with 終わる or similar verbs.
楽しみにしていた映画が、ころっとつまらなく終わった。
The movie I was looking forward to ended disappointingly.
adverb
curling up; falling asleep suddenly
Describes curling up into a ball, often like a fetal position, or falling asleep quickly and deeply. Mimetic for a small, round shape or sudden sleep.
寒くて布団の中でころっと丸まった。
It was cold, so I curled up into a ball under the futon.