Seven-Eleven, the defining features are:
• stanzaic, any number of couplets.
• syllabic, mixed or irregular 7 and 11 syllabic line. 7-7 7-11 11-11 11-7 etc or 7-11 7-7 11-7 11-7 11-11 or whatever combination at the discretion of the poet. (although L6 and if there is a L11 are always 11 syllables.)
• rhymed, consonant-full rhyme
Pasted from http://www.poetrymagnumopus.com/index.php?showtopic=1026#seven
My thanks to Judi Van Gorder for years of work on this fine PMO resource.