A chemical compound (such as potassium bromide), added to a developer to prevent fogging(noun)
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Use "restrainer" in a sentence
"A restrainer is the organizational equivalent of tripping a runner in a foot race - the more often they are tripped, the poorer their performance will be."
"The pencil-thin fire-spouter and the sleazy-looking "restrainer" had a sufficiently unfamiliar air to go with Maulbow's story; but as far as"
"Such names are _mashmashu_, the general term for 'the charmer'; _kalû_, so called, perhaps, as the 'restrainer' of the demons, the one who keeps them in check; _lagaru_, a synonym of kalu; _makhkhû_,"