Mongolian spot

noun1

1. •
   A benign, flat, congenital, usually blue to blue-black birthmark on the lower back with wavy borders and irregular shape, prevalent among East Asians, South-East Asians, Central Asians, Siberians, Polynesians, Native Americans and East Africans. It normally disappears three to five years after birth and almost always by puberty.

   • Mongolian spot is an unfortunate name for this common, benign skin discoloration. Present at birth, mongolian spots are blue-gray or blue-green and represent areas of dermal melanocytosis. — 2004