Relating to, having the nature of, or resembling something that is cylindroid (nearly or roughly cylindrical).
From 'cylindroid' + suffix '-al' (relating to or pertaining to), extending the cylindroid concept into an adjectival form commonly used in technical descriptions.
This is basically the 'adjective form of almost-a-cylinder'—it's the word geologists use when a rock formation is kind of tube-shaped but clearly doesn't care about precision!
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