Since it’s widely believed that Christopher Columbus “discovered” America in 1492, Pre-Columbian refers to everything in the history of the Americas that came prior to the influence of the Europeans. Olmec, Teotihuacan, Toltec, Inca, Aztec, Maya, and countless other native American tribes are examples of the Pre-Columbian civilizations that had their their own art, culture, food, music, tools, beliefs, etc., all free from European influence.
There is some credibility to the belief that the Vikings visited North America, what is now Maine and Newfoundland, as far back as the 10th century, long before Columbus. However their influence was little if any, with the true European influence starting after Columbus’s fateful voyages, which is why we don’t refer to this period as Pre-Viking.