1. A financial instrument that has been publicly traded in the secondary market long enough to eliminate any short-term effects from its initial public offering. 2. Any security that has been issued and actively traded in the Euromarket for at least 40 days. Taobiz explains Seasoned Security 1. When new securities are first offered through an initial public offering (IPO), they can exhibit substantial volatility immediately following their listing. Seasoned securities have already been on the market for a while, making them more predictable than newly-listed securities due to price and trading volume stability. 2. Before the sale of a Euromarket security can be made to certain U.S. investors, the security must trade on the market for a minimum of 40 days.