Supercalifragilisticexpialidocious, typically spelled as one word, is a song from the acclaimed movie Mary Poppins. This particular movie with Julie Andrews, made in 1964 popularized this song as a fun and whimsical song.
Extraordinarily enough, this word was also the subject of a lawsuit. It is alleged that the creators of the Mary Poppins Movie infringed upon copyright laws. The plaintiffs held that it was too close to their song copyrighted in 1951. This particular idea since this word was also the subject of another song in a previous movie, Super, in 1949. The lawsuit brought in 1965 was unsuccessful.
This word, according to the Random House Dictionary 2016 Edition, is an adjective and is a nonsense word used by children to express approval or to represent the longest word in the English language. The word was first added to the Oxford Dictionary in 1986 as its popularity from the 1964 Movie was on a recent rise.
To date there have been many variations on this word, however the song from the movie, Mary Poppins, is still the most popular.