A form of poem, also called a double dactyl, in which most of the eight lines are made up of two dactyls. The name "higgledy-piggledy" is the most common first line of such poems, although "jiggery-pokery" and other nonsense phrases often appear. The second line should, and generally does, name the subject of the poem.

Veteran logophile Jed Hartman explains the rest of the structure:

    The third line can be any old pair of dactyls, usually beginning to describe or discuss the subject given in the second line. The fourth line is truncated, missing the last two syllables of the second dactyl -- it goes "DA-da-da-DA" instead of "DA-da-da DA-da-da."

    The fifth and seventh lines are unrestricted other than by meter, like the third line. The sixth line should ideally be a single six-syllable double-dactylic word, usually an adverb or adjective. And finally, the eighth line is truncated like the fourth line, and rhymes with the fourth line. (No other lines need to rhyme.)

Here's an original example of a higgledy-piggledy:

That higgledy-piggledy is pretty close to the definition, but as in most doggerel you can bend the rules very slightly. Here's another that takes a few liberties:

(Line six would be better if it were a single word, but I think this one has merits other than technical perfection.)

SOURCE: http://www.kith.org/logos/words/lower/d.html