What does over active ovary mean?

Hyperstimulation: There is no such thing as a naturally occurring over active ovary. Perhaps as ovaries get older they experience the body's last attempts at fertility by being hyperstimulated by pituitary fsh to release more eggs (why twins more common with later age), but that's unlikely what you mean. Sometimes fertility md's will artificially stimulate as well, but this can be dangerous if not done carefully.