A dactyl is a term used in formal English poetry to describe a trisyllablic metrical foot made up of one stressed syllable followed by two unstressed ones. Matador, realize, cereal and limerick as well as the word poetry itself are examples of words that are themselves dactyls. A double dactyl can therefore simply mean two consecutive dactyls.
A double dactyl is also a verse form, also known as "higgledy piggledy", purportedly invented by Anthony Hecht and Paul Pascal in 1961, but having a history as a parlor word game earlier in the century. Like a limerick, it has a rigid structure and is usually humorous, but the double dactyl is considerably more rigid and difficult to write. There must be two stanzas, each comprising three lines of dactylic dimeter followed by a line with a dactyl and a single accent. The two stanzas have to rhyme on their last line.
The first line of the first stanza is repetitive nonsense. The second line of the first stanza is the subject of the poem, a proper noun (marked in these examples with a single asterisk, *, or where not exactly a proper name with a parenthesized asterisk (*)). Note that this name must itself be double-dactylic. There is also a requirement for at least one line of the second stanza to be entirely one double dactyl word, for example "va-le-dic-tor-i-an" (marked with two asterisks, **). Some purists still follow Hecht and Pascal's original rule that no single six-syllable word, once used in a double dactyl, should ever be knowingly used again.
A self-referential example by Roger L. Robison:
Dactyls in dimeter,(*)
Verse form with choriambs
One sentence (two stanzas)
Challenges poets who
Don't have the time. (Source: Wikipedia)
Dedicated to Ms Moore (Double Dactly)
Enlivened due to a
(c) Lawrencealot - May 22, 2012
The 6th line above is an invented portmanteau created by inserting the common crude cultural expletive "fucking" inside of the existing word "fantastical".