whale's tail

noun2

1. •
   (slang) An alternative expression of the whale tail phenomenon where a thong peeks out above the waistband.

   • Another distraction occurs when pants ride low in the back and expose thong underwear, a phenomenon students have dubbed whales' tails... — 2004
2. •
   (slang) The distal bifurcation of the left anterior descending coronary artery.

   • It then bifurcates distally and tapers out as a "whale's tail" at the cardiac apex, although sometimes it wraps around the apex to supply part of the inferior wall. — 2007