what does the poetry term 'vulgate' mean, I can't find any definition that correlates to poetry

These definitions could apply to poetry.

The common speech of a people; the vernacular.
A widely accepted text or version of a work.

http://dictionary.reference.com/browse/vulgate

"The Cremation of Sam McGee" is a good example of vulgate poetry -- written in the common speech of some people.

http://www.potw.org/archive/potw22.html

The term "vulgate" is not typically associated with poetry. However, if you are referring to its usage within the context of poetry, it could be a specialized or uncommon term. In such cases, it can be challenging to find specific definitions in standard dictionaries.

In situations like this, it can be helpful to approach the term from a broader perspective. Here's a step-by-step approach you can follow to gain a better understanding:

1. Research standard definitions: Start by searching for the general definition of the term "vulgate" in reputable dictionaries. While it might not directly relate to poetry, this step can provide a foundation for understanding the term's overall meaning.

2. Explore literary dictionaries: Look for specialized resources or literary dictionaries that focus on poetic terminology. These sources might provide alternative or extended definitions of the term.

3. Consult scholarly articles or books: Academic sources can provide detailed explanations and analyses of rare or niche poetic terms. JSTOR, Google Scholar, or university library databases may have relevant articles or books discussing the term "vulgate" in the context of poetry.

4. Consider historical or cultural contexts: In some cases, terms might have unique connotations or meanings within specific historical periods or cultural contexts. Exploring poetry from a particular era or region might shed light on the term's usage.

5. Seek expert opinions: Engage with poetry enthusiasts, scholars, or teachers who might have encountered the term "vulgate" before. Online forums, poetry groups, or social media platforms dedicated to literature can be helpful resources for seeking expert opinions.

By following these steps, you can embark on a comprehensive research process to understand the usage and meaning of the term "vulgate" in the context of poetry.