If you reel, or your mind or brain reels, you feel very confused or shocked and unable to act.

中文解释

发蒙;感到眩晕 We were reeling (in amazement/shock/delight, etc.) from/with the news that we had won all that money. 得知赢了那么多钱，我们都（惊愕得／震惊得／高兴得）发蒙了。