1) Hydroid 2) Hydrozoan 
• (n.) Any species of Sertularia, or of Sertularidae, a family of hydroids having branched chitinous stems and simple sessile hydrothecae. Also used adjectively.
Ser`tu·la'ri·an noun (Zoology) Any species of Sertularia, or of Sertularidæ , a family of hydroids having branched chitinous stems and simple sessile hydrothecæ. Also used adjectively. 
[n] - feathery colony of long-branched stems bearing stalkless paired polyps
noun feathery colony of long-branched stems bearing stalkless paired polyps