whale tail
n.— «Even though I work out in a thong, my G-string always remains discretely tucked beneath the waistband. Despite my love of the G, I hate when girls let their “whale tails” creep out of their paints—I’d give out citations for that offense, too, if I could.» —by Jessica Kaminsky I Hate the Gym Dec. 28, 2004. (source: Double-Tongued Dictionary)
Further reading
What if, instead of being an inanimate object, a dictionary were alive? That’s the idea behind a lavishly illustrated new children’s book called The Dictionary Story (Bookshop|Amazon) by Oliver Jeffers and Sam Winston. This is part of a...