Medical Definition of valerian
1: any of a genus (Valeriana of the family Valerianaceae, the valerian family) of perennial herbs many of which possess medicinal properties
2: a preparation of the dried rhizome and roots of the garden heliotrope (Valeriana officinalis) that is used as an herbal remedy and is held to be beneficial in treating nervousness and insomnia—called also valerian root
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