peridinium
noun
peri·din·i·um
ˌperəˈdinēəm
1
capitalized : the type genus of Peridiniidae comprising marine and freshwater dinoflagellates that are typically subspherical to ovoid in outline and that sometimes have the test prolonged into short horns compare ceratium
2
plural peridiniums
-ēəmz
or peridinia -ēə
: any flagellate of the genus Peridinium 
Word History
Etymology
borrowed from New Latin, borrowed from Greek peridīn-, base of peridīneîn "to whirl, spin around" (from peri- peri- + dīneîn "to whirl, spin about") + New Latin -ium -ium
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- roller-backer
- roller-blind shutter
- roller-coaster
- roller-coat
- roller-skate
- roller-skated
- roller-skating
- roller-top
- roller-up
- rollerballs
- Rollerblade
- rollerbladed
- rollerbladers
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- rollerblading
- rollercoasters
- rollerman
- rollermen
- rollers
- rollers-up
- rollerskatings