What is the word that means bitter of speech?

There are a few words that can describe someone who is bitter of speech, depending on the specific nuance you want to convey:

Formal:

* Acerbic: This word implies a sharp, biting, and often sarcastic tone.

* Caustic: This word suggests a burning, corrosive, and deeply critical nature.

* Sardonic: This word refers to a mocking and cynical tone, often tinged with bitterness.

Informal:

* Biting: This word is a more general term for speech that is sharp and critical.

* Scathing: This word implies a severe and withering criticism.

* Snarky: This word refers to a sarcastic and often mean-spirited tone.

* Sour: This word suggests a general negativity and pessimism in speech.

The best word to use will depend on the specific context and the intensity of the bitterness you want to convey.