triskaidekaphobia \tris-ky-dek-uh-FOH-bee-uh\, noun:
Fear or a phobia concerning the number 13.
Thirteen people, pledged to eliminate triskaidekaphobia, fear of the number 13, today tried to reassure American sufferers by renting a 13 ft plot of land in Brooklyn for 13 cents . . . a month.
-- Daily Telegraph, January 14, 1967
Past disasters linked to the number 13 hardly help triskaidekaphobics overcome their affliction. The most famous is the Apollo 13 mission, launched on April 11, 1970 (the sum of 4, 11 and 70 equals 85 - which when added together comes to 13), from Pad 39 (three times 13) at 13:13 local time, and struck by an explosion on April 13.
-- "It's just bad luck that the 13th is so often a Friday", Electronic Telegraph, September 8, 1996
Despite NASA's seemingly ingrained case of triskaidekaphobia, which forced managers to impose the bizarre, '13-free' numbering system on its flights, the crew of perhaps the most important Shuttle mission to date clearly were unsure if STS-41C was supposed to be unlucky or not.
-- Ben Evans, Space Shuttle Challenger: Ten Journeys into the Unknown
Triskaidekaphobia is from Greek treiskaideka, triskaideka, thirteen (treis, three + kai, and + deka, ten) + phobos, fear.