Any of a class (Enteropneusta) of hemichordate, wormlike animals that inhabit shallow burrows in mud or sand flats of intertidal zones and are equipped with an acornlike proboscis used for digging and collecting food.
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acorn worm — any of several burrowing, often brilliantly colored hemichordates of the class Enteropneusta, usually found in intertidal sand and mud, having an acorn shaped proboscis and collar. Also, acornworm. [1885 90] * * * ▪ hemichordate also called… … Universalium