Mordant is an adjective that means having a sharp or critical manner.
You may have heard the word mordacious used to describe a dog inclined to bite. Our word of the day is also derived from the word bite. Both words come from the Latin word Mordere (MORE dair ay) which means — you guessed it — bite. But our word of the day is more likely to be used figuratively, as in: Shelly’s mordant wit doesn’t always go over so well with her teachers. They don’t find her biting remarks to be helpful in the classroom.