contra proferentum是一个英美法术语，《英汉法律用语大辞典》中给出的释义为“不利解释规则”，不利起草人解释原则，也拼写为contra proferentes。

英文释义可参考Investopedia给出的解释：

The contra proferentem rule is a legal doctrine in contract law which states that any clause considered to be ambiguous should be interpreted against the interests of the party that created, introduced, or requested that a clause be included. The contra proferentem rule guides the legal interpretation of contracts and is typically applied when a contract is challenged in court.

具体的使用场景可参考如下双语例句：

The contra proferentum rule shall not apply to the interpretation of this Contract.

不利解释规则不适用于本合同的解释。

再来了解一下contra，contra一词表示“相反（地）；反对（地）；逆；反向”。如contra legem表示“背离法律，违反法律”。

参考

《英汉法律用语大辞典》（第2版），宋雷

Investopedia