To simplify or otherwise revise in order to appeal to someone of less education, taste, or intelligence. This slangy expression dates from the first half of the 1900s. Publishers Weekly used it in a review of The Business of Books by André Schiffrin: “. . . the attempt to appeal to the lowest common denominator of taste, which has, he says, led network television and movies in such depressing directions, has dumbed down publishing to an alarming degree” (Aug. 21, 2000).