Whale tail is the Y-shaped rear portion of a thong or G-string when visible above the waistline of low-rise pants, shorts, or skirts that resembles a whale's tail.[1][2][3] The fashion was popular in the early 2000s and waned within the decade, but has become more fashionable in recent years.
Low-waisted trousers, such as low-rise jeans or hip-huggers, and higher-cut thongs led to greater exposure of the whale tail.[1][4] The trend was also associated with the trend of sporting lower back tattoos.[5]
The word was selected by the American Dialect Society in January 2006 as the "most creative word" of 2005.