The Collaborative International Dictionary of English v.0.48:

Alcyonacea \Al`cy*o*na"ce*a\, n. pl. [NL.] (Zool.)
   A group of soft-bodied Alcyonaria, of which Alcyonium is
   the type. See Illust. under Alcyonaria.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Alcyonacea
    n 1: comprising the soft corals [syn: Alcyonacea, suborder
         Alcyonacea]