What does it mean if a USB drive takes very long to eject? On a MacBook, I dragged my USB drive to trash icon, and it took at least 5 minutes to eject. It also often takes multiple tries to eject. Does this mean it is corrupted?
Yes, I would think so. If there is no alert hiding somewhere that says that the disk is in use, it very likely corrupted.

I would make a backup and replace the drive as soon as possible.