octosyllable n 1: a verse line having eight syllables or a poem of octosyllabic lines
Octosyllable \Oc"to*syl`la*ble\, a. Octosyllabic. [1913 Webster]
Octosyllable \Oc"to*syl`la*ble\, n. A word of eight syllables. [1913 Webster] octothorp