• Word of the Day from M-W: mordacious
1 : biting or given to biting; 2 : biting or sharp in manner or style : caustic

The Earl of Carnarvan, referred to in 1650 as "mordacious," didn't go around biting people; it was his "biting" sarcasm that inspired that description. The word's association with literal biting didn't come up until later, occurring first in an 18th-century reference to "mordacious" bats. The "caustic" sense of "mordacious" is the more frequent use these days, but admittedly, neither sense is especially common. If you prefer a less esoteric option you can choose "mordant," a synonym that sees a bit more use. Both adjectives descend from Latin "mordere," a verb meaning (literally) "to bite or sting." If you want to sink your teeth into more "mordere" derivatives, you might use "mordacity" to refer to a biting quality of speech, or substitute "mordancy" for "incisiveness" or "harshness."