Greetings, y'all.
Larry gives a pretty fair summary of cinquain here. I had wanted to add something myself the other day when I read all of this for the first time, so I was glad that Larry filled in some of the blanks, so that I don't need to.
I've personally written scores of the Crapsey type of cinquain and probably a few of the 'modern' cinquains, but I'd really never heard of 'cinquain' outside of that context. Larry's identifying the quintain, and my own realization of why there seems to have been a confusion, prior to reading what Larry wrote, can be summed up in this:
Cinquain as a FORM, traditionally, has been considered to refer to the Crapsey type of poem or offshoots of it.
Cinquain or Quintain, as a STANZA, refers to
ANY five-line STANZA, either rhyming or unrhyming....
so that, for example, the FORMS cinquain, tanka, limerick are all quintains
So if one chooses to rhyme it with a particular rhyming pattern, metrical pattern, or whatever, I suppose could be construed as the invention of a new form, but I personally don't see it as such myself....
I've written dozens of SONNETS that have variations of the traditional rhyming patterns, neither English, Spencerian, Italian or whatever, but I honestly don't think that my variants warrant my giving it a new name. I suppose if dozens of others jumped on the bandwagon and followed my lead, then I'd have created a new "FORM".... but short of that, I could only say that I was playing with a form that was already there.....
In THIS case, our colleague has given us some nice options of playing with the STANZA called quintain or cinquain.... but the poetry world will likely not call this a FORM, and will not likely give it the name "Cinquain" since that name is pretty well established already....
and I think it's been written on a good deal here in Karnak somewhere as well.
deLighting in the stimulating discussion, Daniel

P.S. Just looked up that place I mentioned. You might all enjoy looking at the fun we all had with
CINQUAIN