Introduced originally in 1985 by New Formalist, American poet Brad Leithauser.
It has been quite popularized. I find no formal specifications, so interpret as follows.
One word per line
Consists of three quatrains plus a couplet
Volta at poets option.
I feel that to use other than an established sonnet rhyme pattern would be neglect.
Diligent Shopping ( Word Sonnet)
(c) Lawrencealot – November 18, 2012
Volta at 13 (sneaking into it at 12)