A person who demurs; someone who objects or raises an objection, especially in a legal context.
From the present participle of demur plus the agent suffix -ant, which creates nouns for people who perform an action. This is a rare or legal-specific variant.
In old legal documents, a demurrant would file what's called a 'demurrer'—basically saying 'your case doesn't hold up legally' without even arguing the facts!
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