Antonyms for the term "firming a deal" would refer to actions or attitudes that create ambiguity, uncertainty or conflict. These could be negotiating in bad faith, changing terms at the last minute, being indecisive or uncommitted, or even showing signs of hostility or disrespect towards the other party. In contrast to "firming a deal," antonyms could refer to practices that are impractical, counterproductive or even illegal, such as lying, cheating, misrepresenting facts, or breaking trust. Therefore, it is essential to adopt ethical and transparent practices when engaging in negotiations to build trust, rapport and ultimately close deals that benefit all parties involved.