Real Dictionary

avidin in American English
a protein in raw egg white that binds to biotin, making the biotin inactive in the body
noun: 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

avidin in British English
noun: a protein, found in egg-white, that combines with biotin to form a stable compound that cannot be absorbed, leading to a biotin deficiency in the consumer