Jingwei (simplified Chinese: 精卫; traditional Chinese: 精衛; pinyin: jīngwèi) is the name of a character in Chinese mythology. Originally the daughter of the emperor Yandi, she perished at a young age in the East Sea. After her death she chose to assume the shape of a bird in order to exact revenge upon the sea by bringing stones and small twigs from the mountains nearby over the sea in an effort to fill it up. Jingwei even has a short dialogue with the sea where the sea scoffs her, claiming that she wouldn’t be able to fill it up even in a million years, whereupon she claims that she will then proceed to take ten million years, even one hundred million years, whatever it takes to fill up the sea so that others would not have to perish as she did.

From this myth comes the Chinese expression 精卫填海 (”Jingwei filling the sea”) meaning a symbol of dogged determination and perseverance in the face of seemingly impossible odds.

Source: http://en.wikipedia.org/wiki/Jingwei