1. of, relating to, or denoting the earliest period of Earth's history, before the Cambrian period, spanning from the formation of Earth to about 541 million years ago
Usage: geology; often capitalized

1. the Precambrian eon or era; the earliest major division of geological time
Usage: geology; often capitalized

Examples

• Precambrian rocks make up the oldest parts of Earth's continental crust.
• The Precambrian eon lasted for about 4 billion years.
• Fossils are rare in Precambrian deposits because early life forms had no hard shells.
• Geologists study Precambrian geology to understand the early development of our planet.
• The Precambrian ended with the Cambrian explosion, when complex life forms rapidly diversified.
• Most of Canada's landscape is built on Precambrian bedrock.