terza rima

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A verse form of Italian origin consisting of tercets of 10 or 11 syllables with the middle line rhyming with the first and third lines of the following tercet.

Century Dictionary and Cyclopedia

1. n. A form of verse in iambic rhythm used by the early Italian poets. In it the lines consist of ten or eleven syllables, and are arranged in sets of three that are closely connected. The middle line of the first tiercet rimes with the first and third lines of the second tiercet, the middle line of the second tiercet rimes with the first and third lines of the third tiercet, and so on. At the end of the poem or canto there is an extra line which has the same rime as the middle line of the preceding tiercet. In this form of verse Dante's “Divina Cormmedia” is written. The most conspicuous example of its use in English literature is Byron's “Prophecy of Dante.”

Wiktionary

1. n. A type of poem with verses of three lines and a rhyme scheme: aba bcb cdc.

GNU Webster's 1913

1. A peculiar and complicated system of versification, borrowed by the early Italian poets from the Troubadours.

WordNet 3.0

1. n. a verse form with a rhyme scheme: aba bcb cdc, etc.