Mordacity is a term used to describe a biting and sarcastic demeanor. Synonyms for mordacity include acerbity, sarcasm, cynicism, keenness, biting wit, and causticness. Acerbity and causticness specifically refer to a sharp and critical tone. Sarcasm, cynicism, and biting wit describe a tone that is sharply amusing or satirical. Keenness refers to a tone that is sharply perceptive or decisive. All of these synonyms convey a sense of negativity and criticism, but they vary in degrees of humor and insightfulness. Ultimately, the choice of synonym depends on the context in which it is used and the intended audience.