The term "most smart mouthed" refers to someone who tends to speak in a way that is considered witty, sarcastic or even insulting, often in an attempt to be humorous. Synonyms for this phrase would include "quick-witted", "clever-tongued", "sharp-tongued", "sardonic", "acerbic", "caustic", "ironic", "satirical", and "snarky". These terms all convey a similar idea of someone who speaks with a certain degree of intelligence, humor, or sarcasm, but may also carry negative connotations in terms of their delivery. Ultimately, the most fitting synonym for "most smart mouthed" will depend on the context and tone of the person's speech.