n. Physics & Chem. Density. A non-existant or ghost-word originating from mistakes in Webster's New International Dictionary editions 1934-1939. Original entry should have been "D or d" in the abbrevations section, when something messed up.
the best word in the history of the English language. this word should be put back in the dictionary and should encompass not only density in the scientific sense but should also be used to describe a dumb person.