A parasitic worm that lives within the body cavity or coelom of its host organism.
From coelom (Greek koilos 'hollow') plus helminth (Greek helmins 'worm'), directly describing parasitic worms inhabiting hollow body spaces.
Parasites are so specialized that scientists invented separate names for where they hide—coelelminth for cavity-dwellers versus entoelminth for intestinal worms—showing how parasitology demanded its own vocabulary.
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