Dihydrogen monoxide

DHMO stands for dihydrogen monoxide, a technically accurate but never used term for water that is a running joke among chemists, environmental activists and others, to illustrate how general ignorance of science can lead to wildly misplaced fears.

The joke involves describing water and its effects as if it were an exotic chemical with dangerous properties, e.g.: "This odorless, tasteless chemical kills thousands of people a year, due to both overconsumption and underconsumption. And it is involved in problems small and big: Virtually all cancerous growths contain dihydrogen monoxide in biologically significant amounts, and it is also the enabling component of both acid rain and most soil erosion!"