The 31-year-old blonde beauty looked her usual stunning self as she flashed her slender pins in a daringly short red dress, which featured cheeky keyhole cut-outs that showed off a glimpse of her décolletage.
As Moose 'The Moose' Rosser and Sam Green faced off in a letters round, the luck of the draw brought up the opportunity for some rather racy words.
After The Moose announced his six-letter find of "erotic", Sam stifled a giggle before declaring his: "Coming".
Rachel Riley stunned in a daringly short red frock
She flashed her slender pins in the tight-fitting number Rachel Riley in pictures Fri, March 3, 2017
Rachel Riley is the Carol Vorderman of the naughties. She co-hosts Countdown and here are some of her best pictures
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Rachel Riley steals the show in baby blue dress
Host Nick Hewer, 73, ignored the combination, his expression blank as he handed the challenge over to Dictionary Corner.
There, however, the innuendo didn't go unnoticed, as BBC Breakfast's Dan Walker, 40, fought to retain his composure, saying: "What a peculiar combination that is.
"There is an eight in there – as we move swiftly on," he added. "Intercom."
The camera then cut to Rachel Riley, who rearranged the letters on the board to spell out the eight-letter word, catching her struggling to keep a straight face after the hilarious double entendre.
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Dan Walker tried to keep a straight face at the racy innuendo
Rachel smirked as the contestants spotted a saucy combination of words
Eariler in the show, the word "gonads" appeared again, having been pointed out by Countryfile star Adam Henson, 51, only a few weeks ago.
Her professionalism was also put to the test just days earlier, when she had to spell out the word "squirter" when a contestant spotted the high-scoring find on the letters board.
Countdown airs weekdays at 2.10pm on Channel 4.