Question: What is the longest word in Spanish?
Answer: The answer depends on what you mean by the longest word, but regardless of your definition the longest word isn't superextraordinarísimo, the 22-letter word once listed in a famous recordbook and the word that was usually cited as the longest in the language. (It means "most superextraordinary.")
The designation of superextraordinarísimo seems arbitrary at best. For one thing, the word isn't in real use. When I first researched this article in 2006, a Google search showed not a single instance where the word was used on a Spanish-language website — except on pages listing what they called the longest Spanish words. (Since I write the original version of this article, claims of superextraordinarísimoit being the longest word have mostly disappeared.) And superextraordinarísimo has two other strikes against it: If one is going to create words by adding prefixes and suffixes, one could just as well make a 27-letter word by using the adverbial form, superextraordinarísimamente. Or one could just as easily use longer root words, ending up with words such as superespectacularísimamente ("most superspectacularly"). But again they're hypothetical words rather than ones that get legitimate use.
A better choice for a 22-letter word is esternocleidomastoideo, the name of a certain neck muscle. It can be found in Spanish-language medical texts.
But we can do better without coining words. The longest words to be found in general publications appear to be two 23-letter beauties: anticonstitucionalmente ("unconstitutionally") and electroencefalografista ("electroencephalograph technician"), the latter also appearing in the Spanish Royal Academy's dictionary. Since the latter is a noun, it can be made a 24-letter plural, electroencefalografistas, my designation as the longest legitimate Spanish word. Although it's not an everyday word, you can find it in encylocopedias and some phone directories.
Of course, there's always the 32-letter nonsense word supercalifragilisticoexpialidoso, the Spanish transliteration of "supercalifragilisticexpialidocious," which appears in Spanish versions of the Walt Disney musical Mary Poppins. However, that word's use is essentially limited to the film and play.
By coining cognates of some especially long English words, it would be possible to come up with longer words still. For example, some medical words and names of some chemicals in English top 30 letters, and the longest English word listed in an accepted dictionary is reported to be "pneumonoultramicroscopicsilicovolcanokoniosis," a type of lung disease. Conversion of the word to Spanish, made easy by the fact that all the roots have Spanish cognates, presumably would be neumonoultramicroscopicosiliciovolcanconiosis at 45 letters, or something similar. But such words are best spurious rather than legitimate Spanish.