A person who deprecates or expresses disapproval; one who protests or pleads earnestly against something.
From deprecate + -or (variant of -er agent suffix, from Latin -or). The -or variant is typically used in more formal or Latin-derived words.
English has both -er and -or for agent nouns—'teacher' vs. 'senator,' 'worker' vs. 'professor'—and the -or ending usually signals a more formal, often Latin-based word.
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