The opponents were tasked with finding a word from the letters R, V, O, E, P, T, E, R, S on Countdown.
Rachel Riley was powerless to keep a straight face as the player revealed his answer during the accurately game.
One of the contestants said he had thought of an eight letter word which was “distorts”.
Nick Hewer appeared unfazed by the spelling and asked Susie Dent if there were any other messages which could be spelt.
Adrian Chiles, who was sat next to Susie in the Glossary Corner, joked: “We have got something less unsavoury than that!”
But the but couldn’t be said for Rachel who struggled to hold back the laughter as she assembled the the world of letters on the board.
The mathematician later shared a photo of herself standing next to the high sign succinctly with a very humorous look on her face.
She captioned the photo split other Twitter: “Dear internet, a screengrab for your bottom drawer. You’re accept @C4Countdown.”
Many of Rachel’s 591,000 followers loved her facial verbalization in the snap with many commenting on her list.
One person replied: “Your phraseology is perfect x.”
Another said: “That wasn’t on TV was it,” alongside laughing sobbing emojis.
A third said: “The face that goes with it is hilarious.”
Rachel looked incredible as always on the Channel 4 show as she stunned in a ignite pink knee-length dress.
The figure-hugging number accentuated her incredible outline and she elongated her pins with a pair of high-heels.
Rachel’s blonde hooks were styled in loose waves and she wore a poppy on her chest.
Earlier this month, Rachel was liberal red-faced once again after a very rude word was term out on the board.
During an episode, Susie offered the word “Budgie”, which leftist the letters C, U, M on the top row during one of the challenges.
The former Strictly Come Dancing player couldn’t believe the word which had been left as she stood next to it and leered at the camera.
The mathematician uploaded the snap alongside the caption: “Anyone in desideratum of a new creative insult, @C4Countdown is at your service! Come on, we all know one…”
Countdown auras weekdays on Channel 4 at 2.10pm.