Nucular is an alteration of the word nuclear which represents the commonplace [ˈn(j)uːkjə.lə(ɹ)] (in IPA) pronunciation of that word instead of [ˈn(j)uː.kli.ə(ɹ)] or [ˈn(j)uː.kli͡ə(ɹ)].
This pronunciation is especially common in the U.S. Southern states, and the pronunciation is a revealing cultural shibboleth.
It is disapproved of by some who consider it a mispronunciation, although most influentual dictionaries recognize it to some extent.
Merriam-Webster dictionary:
Oxford English Dictionary:
American Heritage Dictionary:
Merriam-Webster receives enough questions about their inclusion of this pronunciation in the dictionary that it is one of two pronunciations which receive particular mention in their FAQ (along with "February"). [1]
US Presidents Dwight D. Eisenhower, John F. Kennedy, Gerald Ford, Jimmy Carter, Bill Clinton, and George W. Bush (but not his father, George H. W. Bush) have all used this pronunciation. Jimmy Carter in particular had served as an officer on the United States Navy's first experimental nuclear submarine, and would have been well exposed to both pronunciations.
It has been also used by British Prime Minister Tony Blair.
The reason why nuclear becomes nucular is founded in the phonotactics of the English language.
This is probably influenced by other adjectives in the science technical terminology that end in -cular (molecular, particular etc.).
"Nucular" is also the pronunciation preferred by Homer Simpson, and his confident use of it in The Simpsons exemplifies a level of cultural information that is largely overheard at some distance, second-hand, rather than read.
Also the entire argument was parodied on one episode of Family Guy, in which Peter says to his wife, "Haha! You said nuclear, it's nucular dummy, the 's' is silent".