Having the quality, appearance, or characteristics resembling gunpowder; containing or composed of gunpowder-like material.
From 'gunpowder' plus the suffix '-ous' meaning full of or characterized by. This is a less common adjectival form created to describe things that resemble or contain gunpowder.
This is one of those words that exists but sounds archaic or made-up—it would appear in old chemistry texts or Victorian-era writing describing the smell or appearance of explosive materials, giving those descriptions an oddly poetic quality.
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