The
German word for "
oxygen tank".
Also, the only word which would require an f-f-f-l ligature to print. This causes typeface designers to face a dilemma: do they make a special character for this one word, or do they let it be printed as "f ffl" and look a bit odder than it already is?
Source: "A Collection of Word Oddities and Trivia", http://members.aol.com/gulfhigh2/words7.html