Aunt Flo is a euphemism for a menstrual period. Years ago, talking about menstruation in mixed company was taboo. Women came up with other words and phrases for a period, such as a monthly visitor or a visit from Aunt Flo. On the internet, Aunt Flo is often shortened to AF. However, AF also has other meanings online, such as alcohol-free. Other euphemisms for menstruation include: Carrie (from the movie of the same name) Crime scene or CSI Crimson tide Moon time Mother nature's gift On the rag Rag week Red wedding Riding the cotton pony Shark week That time of the month