Term used to describe the visible part of a thong on a chick's butt when worn with low rise pants - resembles a whale's tail. (I say chick because I don't want to see a guy wearing this.)
whale tail – the appearance of the top rear strap of a woman’s thong, v-string or g-string underwear above the waistline of her pants, shorts, or skirt whenever she sits, bends over or squats, though some low-rise clothing is now designed to display the whale tail at all times; so-called because the strap closely resembles a whale’s tail rising from the water.
the portion of a thong that shows above the pants in the back, it resembles a whale tail. whale tail- when a girl bends over and previously unseen whale tail shows, she is whale tailing, you the one who sees it have been whale tailed.
When Annette bent over half of her thong was visible. " Yo, Annette, you just whale tail(ed) me, son!"