A spokesperson for the Channel 4 gameshow said the word had been included in "an error of judgement".
The homophobic slur was read out by a contestant as a seven-letter answer to the word quiz, for which he was awarded the points.
Anne Robinson has again made controversial comments about sexual harassment in office environments.
Countdown presenter Nick Hewer has revealed that Colin Murray will step in to replace him on the gameshow while he 'shields at home' during lockdown.
The 'Countdown' host came under scrutiny recently when she wore a top that claimed the Labour MP is a 'racist endeavour.'
The presenter has said she shared a bedroom with her mother and older brother and sister.
The contestant looked pleased with himself as Rachel Riley spelled out the explicit word on the board.
The 'Countdown' presenter is backing a campaign to block trolls after noticing the affect stress had on her unborn child.
A Countdown contestant is being praised by viewers for winning a round of the Channel 4 gameshow by spelling the word “hentai”.
The happy couple shared a picture from Sin City, where they tied the knot at the weekend.