sepiacean,a.andn.Zool.|siːpɪˈeɪʃən| [f.mod.L. Sepiāceus, f. sepia: see -aceous.] Pertaining to, or a member of, the group Sepiacea of cuttle-fishes. Also sepiˈaceousa. 1842Penny Cycl. XXII. 360/2 The borders of the mantle or of the sac of the Sepiaceans.1858Mayne Expos.Lex., Sepiaceus..a sepiaceous.