"Pygmalion" is not a thing to be defined, but rather the name of a character from ancient mythology. According to Ovid's Metamorphoses, Pygmalion was a sculptor who carved the image of a woman so beautiful that he fell in love with her and pleaded with Venus to turn the statue into a real woman. Venus was touched by his plea and granted his wish.
George Bernard Shaw later used Pygmalion as the title of his book about the transformation of a young Cockney flowergirl into a highbrow woman of British society through the efforts of a linguist by the name of Henry Higgins. The play was later popularized as the musical and movie, My Fair Lady.