nottava rimaa stanza of eight lines of heroic verse with the rhyme scheme abababcc
Webster's Revised Unabridged Dictionary
Ottava rima(Pros) A stanza of eight lines of heroic verse, with three rhymes, the first six lines rhyming alternately and the last two forming a couplet. It was used by Byron in “Don Juan,” by Keats in “Isabella,” by Shelley in “The Witch of Atlas,” etc.
Chambers's Twentieth Century Dictionary
Ottava rimaan Italian form of versification consisting of eight lines, the first six rhyming alternately, the last two forming a couplet—used by Byron in Don Juan