William Shakespeare--the 16th-century dramatist and poet, not the 19th-century musical composer and pianist--is credited with using the longest English world faithfully alternating consonants and vowels: the 27-letter HONORIFICABILITUDINITATIBUS. The term is, unfortunately, both a nonce word and obviously Latin, not truly English. The Funk & Wagnalls Unabridged, apparently by way of a back formation, has converted the word into HONORIFICABILITUDINITY, a 22-letter term wholly English in appearance, possessed of a simple meaning ("honorableness"), and also alternating consonants and vowels regularly. Since 1913, when that dictionary was first published, these two words have stood unchallenged in point of length.
Borgmann, Dmitri A.
"The "C-14" Problem,"
Word Ways: Vol. 23
, Article 13.
Available at: http://digitalcommons.butler.edu/wordways/vol23/iss3/13