octosyllabic

• octasyllabic

From octo- +‎ syllabic.

• (Received Pronunciation) IPA^(key): /ˌɒk.təʊ.sɪˈlæb.ɪk/
• (General Australian) IPA^(key): /ˌɔk.təʉ.sɪˈlæb.ɪk/
• (General American) IPA^(key): /ˌɑk.toʊ.sɪˈlæb.ɪk/
• Rhymes: -æbɪk

octosyllabic (not comparable)

1. Containing eight syllables
   • 1872, Ralph Waldo Emerson, Poetry and Imagination:

     If you hum or whistle the rhythm of the common English metres,— of the decasyllabic quatrain, or the octosyllabic with alternate sexisyllabic, or other rhythms, […]

• octosyllable