Like the thong shot the Whale Tail Thong is another one of those picture related terms, it refers to when a g-string is exposed by a woman and you get the shape of the thong which looks like a whale tail. Normally these things happen normal activities like squatting, bending over walking. Be careful though there are web sites that are literally about the Whale Tail Thong which are covered in pictures of women caught showing off there whale tail thong similarly to the shot one they are normally poll type web sites that people vote for there favorite, don't worry though these thankfully don't normally have pictures of any fat people that shouldn't be wearing them with a whale tail thong (lets be honest it could be pretty scary).