[flat-wurm] 
| any worm of the phylum Platyhelminthes, having bilateral symmetry and a soft, solid, usually flattened body, including the planarians, tapeworms, and trematodes; platyhelminth. |
| flat·worm (flāt'wûrm') n. Any of various parasitic and nonparasitic worms of the phylum Platyhelminthes, such as a tapeworm or a planarian, characteristically having a soft, flat, bilaterally symmetrical body and no body cavity. Also called platyhelminth. |
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. |
