The Collaborative International Dictionary
Sea fir
Sea fir \Sea" fir`\ (Zo["o]l.) A sertularian hydroid, especially Sertularia abietina, which branches like a miniature fir tree.
Wiktionary
sea fir
n. A sertularian hydroid, especially (taxlink Sertularia abietina species noshow=1), which branches like a miniature fir tree.