Relating to or containing cinder or ash; resembling or consisting of cinders.
From Latin 'cinis' (ash, cinder) + '-ous' (full of). The root evolved through Old French to describe the ashy or burnt remnants of fire.
This word is so rare that even most dictionaries have dropped it, yet it perfectly captures the state of something burnt to ash—linguistically, it's a fossil word showing how specific and precise older English could be about describing fire's aftermath.
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