When a female of the species is highly intoxicated and casts extremely non discreet, sexually provocative stares toward a male, or multiple males depending on the measure of desperation. The hormonally charged woman is also undoubtedly on her period, which can only be confirmed with a dip stick check of her nethers.
"Dude, this chick on the other side of the bar is totally checking you out." "Nah man, look at her eyes and how she's sitting on that bar stool. She's totally red staggin."