ころりと変かわるto change suddenly and completely
彼かれの態たい度どがころりと変かわった。
His attitude suddenly changed completely.
ころりと忘わすれるto forget something completely, as if it never happened
約やく束そくのことをころりと忘わすれてしまった。
I completely forgot about the promise.
ころりと寝ねるto fall asleep instantly
疲つかれていたのでベッドに入はいるところりと寝ねてしまった。
I was so tired that I fell asleep the moment I got into bed.
ころりと騙だまされるto be easily and completely deceived
彼かれはその話はなしにころりと騙だまされた。
He was completely taken in by that story.
ころりと転ころがるto roll with a light, crisp sound
コインが床ゆかにころりと転ころがった。
The coin rolled across the floor with a light plink.

Related words

ころっと sense 1
ころっと often implies a more abrupt or decisive change, while ころり can feel slightly softer or more effortless.
すんなりN2sense 1
すんなり means 'smoothly' or 'without trouble', but lacks the suddenness or completeness that ころり conveys.
あっさりN1sense 1
あっさり describes doing something easily or without fuss, while ころり adds a sense of sudden, complete change.

Don't confuse with

コロコロN1
ころころ describes repeated or continuous rolling/changing, whereas ころり describes a single, complete instance of change or falling.

Mimetic word derived from the sound or sensation of something rolling or turning over smoothly. The exact origin is uncertain.