duplicity doo-PLIH-suh-tee (noun) : the disguising of true intentions by deceptive words or action Example sentence: Nicole told me that she had been studying all night, but I detected her duplicity; I knew she had gone to the party. Did you know? If someone's duplicity has left you feeling like you're seeing double, take heart in the word's etymology. "Duplicity" comes from a long line of "double" talk, starting with its Latin grandparent "duplex," which means "double" or "twofold." As you might expect, "duplex" is also the parent of another term for doubling it up, "duplicate." And of course, the English "duplex" (which can be a noun meaning "a two-family house" or an adjective meaning "double") comes from the Latin word of the same spelling.