"Bitter words" is a phrase that is often used to describe hurtful or harsh language that can leave a lasting impact on the recipient. However, there are several synonyms that can be used to convey the same meaning, such as acrimonious, cutting, venomous, spiteful, caustic, vitriolic, harsh, scathing, sarcastic, biting, and malicious. These words can be used to describe not only spoken words, but also written or online messages that are meant to hurt or insult. It's important to be mindful of the language we use and how it can affect others, and to strive for kindness and empathy in all our interactions.