Is it permissible to propose to a divorced woman during her 'iddah (waiting period)?

Engagement can be either an explicit proposal or an implicit hint. An explicit proposal for an 'iddah-observing woman is absolutely impermissible. As for an implicit hint, it is permissible for a woman observing 'iddah due to death or an irrevocable divorce. However, it is not permissible for a woman observing 'iddah due to a revocable divorce, because she is still under the legal authority of her husband.