opt inglossary / OPT IN opt in, vb. To choose to participate in (something) (when the choice of settling or not settling came, the Joneses opted in, hoping to avoid a lengthy trial). 词条贡献者 双语律师Philipp,国际知名法学院法律专业,擅长翻译各类与医疗保健相关诉讼相关的法律文件。