When a woman has all the symptoms of her period (bloating, fatigue, mood swings, cravings, cramps) without actually being on her period. Or when she has all the symptoms when shes suppose to be on her period, but her period doesn't show up until two weeks later.
"ugh, my stomach hurts. I feel bloated"
"Are you on your period?"
"No, but I'm suppose to be."
"Ah, must be a ghost period."