回想 (かいそう) literally means “spin thoughts around,” or something like that. 想い (おもい) is, I believe, the direct object of 回す (まわす). Why are they not in the Japanese order (DOをVする)? I think it’s because the compound is Chinese in origin and therefore uses the same grammatical order as English (Subject Verb Object).
A less literal translation gives you “recall, recollect.” The other possibility is “flashback,” which is how I saw it used the other day. Pretty cool stuff.
Pff, compounds including the sound “kai” and using Chinese word order are, like, so last week.
The first (and so far, only) usage I’ve seen this word is when watching TV. As I always watch with the captioning turned on, when there’s a flashback they stick 回想 on top of the captions to let you know that it’s… a flashback.