Eight-year-old Tanmay Dixit brought more blushes from Vorderman and the show's host Richard Whiteley by submitting the seven-letter "fannies" in another round.
Tanmay was taken to watch the show at Yorkshire TV's studios in Leeds as a birthday treat as he is mad on word games.
He only appeared as a contestant on the show after producers said he was too young to be in the audience and they auditioned him there and then.
Tanmay went on to win his contest against a 44-year-old IT trainer.
The precocious youngster, whose parents are both doctors, plays several musical instruments and is two years ahead of his age group at Charlestown Primary School in Manchester.
A spokesman for Countdown said they were always looking for contestants and were happy to have entrants on the show from "eight to 80" years of age.
Tanmay's appearance on the show will be broadcast next Monday.