Curtal Quatrain (French- cut short) is a 19th century American verse form made popular by Archibald Mac Leish. This is not the quatrain used in theCurtal Sonnet of a few of decades before. The sonnet may have influenced the creation of this verse form but the sonnet’s quatrain is 4 lines of iambic pentameter with a trimeter tail added as a 5th line. In the Curtal Quatrain the 4th line is the shorter line.
Curtal Quatrain is:
• stanzaic, written in any number of quatrains.
• metered, primarily iambic. L1, L2, L3 are pentameter and L4 is dimeter.
• rhymed. Rhyme scheme xaxa
Pasted from http://www.poetrymagnumopus.com/index.php?showtopic=622#quatrain
My thanks to Judi Van Gorder for years of work on this fine PMO resource.