The Collaborative International Dictionary
Depolarizer \De*po"lar*i`zer\, n. (Elec.) A substance used to prevent polarization, as upon the negative plate of a voltaic battery.
Wiktionary
n. (context chemistry English) Any substance added to the electrolyte of a battery that produces hydrogen in order to combine with the liberated hydrogen and prevent the build up of pressure.
Wikipedia
A depolarizer or depolariser, in electrochemistry, according to an IUPAC definition, is a synonym of electroactive substance, i.e., a substance which changes its oxidation state, or partakes in a formation or breaking of chemical bonds, in a charge-transfer step of an electrochemical reaction.
In the battery industry, the term "depolarizer" has been used to denote a substance used in a primary cell to prevent buildup of hydrogen gas bubbles. A battery depolarizer takes up electrons during discharge of the cell; therefore, it is always an oxidizing agent. The term "depolarizer" can be considered as outdated or misleading, since it is based on the concept of " polarization" which is hardly realistic in many cases.
Usage examples of "depolarizer".
He then deliberately turned the focus of a protein depolarizer on himself and fell instantly and painlessly dead.
Then she opened a cloth bag she had brought with her and took out a quire of vitron sheets which she proceeded to weave together by rapid, delicate movements of a pair of slender, tetra-faceted depolarizers, whose battery-fed wires made her look as though she were holding a large spider.