Definition of flatworm in US English:



  • A worm of a phylum which includes the planarians together with the parasitic flukes and tapeworms. They are distinguished by having a simple flattened body which lacks blood vessels, and a digestive tract which, if present, has a single opening.

    Phylum Platyhelminthes: several classes

    • ‘Among the earliest hunters, flatworms were simple but effective killing machines.’
    • ‘The initial studies involved little flatworms called planaria that have a very primitive nervous system.’
    • ‘The cestodes, or tapeworms, differ in a number of ways from other flatworms.’
    • ‘Planarians are free-living flatworms, and have a much simpler life history.’
    • ‘All the ponds hosted parasitic flatworms called trematodes.’