- noun an electrolytic or dry cell that has an electrode made of mercury
- A primary cell in which the anode is zinc, the cathode is mercuric oxide, and the electrolyte is a solution of potassium hydroxide. It produces an essentially constant output of 1.35V throughout its useful life, and is usually in the form of a small flat disk. It is used in hearing aids, watches, and other small devices, but is being replaced by other cells due to the toxicity of mercury. Also called zinc-mercuric-oxide cell.