1. A protein found in egg white that inactivates the vitamin biotin.
2. A protein found in uncooked egg white that binds to and inactivates biotin. An abundance of avidin in the diet can result in a deficiency of biotin.
3. A protein, found in the white of egg, that combines with and prevents the action of biotin, thus injuring the animal that consumes it in excess by producing biotin deficiency.
4. Etymology: from the mid-20th century. The element avid is used because of its avidity, or affinity, for biotin.