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| an extraordinary or unusual thing, person, or event; an exceptional example or instance. |
| the offspring of a zebra and a donkey. |
flatworm flat·worm (flāt'wûrm')
n.
Any of various worms of the phylum Platyhelminthes, including the parasitic tapeworms and flukes, characteristically having a soft, flat, bilaterally symmetrical body and no body cavity. Also called platyhelminth.
| flatworm (flāt'wûrm') Pronunciation Key
Any of various parasitic and nonparasitic worms of the phylum Platyhelminthes, characteristically having a soft, flat, bilaterally symmetrical body. Flatworms lack a coelom (body cavity), respiratory system, and circulatory system, but are the most primitive invertebrates to have a brain. The evolutionary history of flatworms is uncertain, but they share some basic characteristics with rotifers, nematodes, and a few other invertebrate phyla. Cestodes (tapeworms), planarians, and trematodes (flukes) are flatworms. |