What is a whale tail slang?

"Whale tail" is a slang term used to describe the appearance of a woman's thong or G-string underwear when it is exposed above the waistband of her pants or skirt, resembling the shape of a whale's tail. This term gained popularity in the early 2000s when low-rise pants were a popular fashion trend, causing many women's underwear to be visible when they bent over or sat down. The term is often used in a derogatory or mocking manner to criticize women for showing too much skin or being inappropriate in their clothing choices.