worthless securityglossary / worthless security A security that has lost its value, for which a loss (usu. capital) is allowed for tax purposes. IRC (26 USCA)§ 165. [Cases: Internal Revenue 3429.] 词条贡献者 双语律师Jason,国内知名法学院国际贸易专业,擅长翻译各类与出口管制、经济制裁及海关相关的法律文件。