Arrayed

[Erthona]

You can have a five foot line based on syllabic verse, which would just mean that each line had five syllables in it, but I don't think you could call that pentameter, especially as in English syllabic verse there are not even hemistichs to act as dividers within the line. So even though I suppose one could call something syllabic pentameter as there is no rule against it per se, it would be fairly nonsensical. Using accentual heptameter as I did, is already stretching it, but to call a line of five syllables, syllabic pentameter, would probably not be accepted by most people. Plus, generally such a designation is not really needed, as it is fairly easy to count the syllables. You could have "pyrrhic pentameter", at least theoretically. Pyrrhic is a foot consisting of two unstressed syllables, so ten unstressed syllables would technically qualify as "unaccented pentameter", however, I can think of no reason why anyone would want to attempt such a thing, outside of, "just because", as it makes no real sense, plus even words that are normally not accented, would begin to take on an accent simply because we are accustomed to hearing one every few syllables. There are many forms that have no real title. Only metered poetry has it's own nomenclature for identifying different types. I'll email you a poem of mine that has an obvious form, but has no name. At least I'm fairly certain it doesn't, seeing as how I made it up
It's a fun form to write in, and not too terribly difficult. Just for fun, I made up a poem form called a "Dique", and later saw it listed somewhere as tho9ugh it were a real poetic form.

Dale