Reminiscence, Recollection
noun, verbal noun, の adjective
The past events revolve around your mind as you imagine them. That's a reminiscence or recollection of those times. 回想 refers to the reminiscence or recollection of past experiences or events. It's often used to describe flashback scenes in movies or dramas, as well as moments in literature where characters think back on their past.
かいそう
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
この映画のこの回想のシーンがすごく好きなんだよね。
I really like this retrospective scene in the movie.
ポールはビーチで、とりとめのない回想にふけっていた。
Paul was lost in aimless reminiscence at the beach.
ビエトが時々、仕事中にヤクザ時代のことを回想しているのを私は知っている。
I know that Viet sometimes reminisces about his yakuza days during work hours.