Ottava rima

What is Ottava rima?

Ottava rima definition and meaning on Dictionary terms:
noun, plural riA.mas.
an Italian stanza of eight lines, each of eleven syllables (or, in the English adaptation, of ten or eleven syllables), the first six lines rhyming alternately and the last two forming a couplet with a different rhyme: used in Keats’ Isabella and Byron’s Don Juan.