Of course, there's another meaning to that turn of phrase that we're all familiar with, and doesn't need outlining fully here.
OK, it refers to female masturbation, are you happy?
Still, 39-year-old Richard Hards thought that the saucy advert was a joke or a fake at first, but clicked through on the link and soon discovered that - in actual fact - it was a genuine Costa advert.
They've clearly thought through their approach to viral marketing then, given that we're all here.
Or, perhaps they're just a little naïve?
In what seems to be a totally legit post from the Dunmail Park of Costa in Workington, Cumbria, they are encouraging people to 'flick the bean', but what they're actually referring to is flicking a coffee bean into a cup in order to win prizes.
Richard, from Surbiton in West London, said: "A friend of mine sent me the post saying 'what on earth are Costa thinking?'
"At first I thought it was a hoax, there was a bit of me that thought 'that can't be real, someone's made that'.
"I did my due diligence, rather than just sharing it, and found the post on Facebook.
"When I saw the phrasing 'flick the bean' I thought 'someone needs to check the definition on Urban Dictionary'.
"I don't know whether [the person responsible] was being a bit cheeky."
"There's a bit of me that hopes it is very tongue in cheek but I think whoever signed it off might not have necessarily got the underlying joke in there.
"It's a bit risqué. It's something I would imagine a smaller company that was trying to get people's attention would run with for a little giggle, but slightly surprised to see it from a national brand like Costa.
"The ad put a very cheeky smile on my face for the rest of the day."
The full post read: "FRESHERS! Fuel your early morning lectures OR the start of your wild nights out with a discounted or even a FREE Costa treat!
"Get lucky when you flick the coffee bean into one of the Costa cups to reveal a surprise deal.
"Play 'FLICK THE BEAN' here!"
The advert post has now been deleted, as well as similar posts from other Costa outlets. The page for the game has seemingly also been deleted from their website, replaced with a page saying they're performing website maintenance.
Richard continued: "I imagine they may have got a bit of flack - a family-friendly company posting things like that.
"It's a little bit on the nose, but I'm a little bit sad to see it come down."
A Costa Coffee spokesperson said: "This competition was run by one of our franchise partners in a small number of stores and was not approved by Costa Coffee.
"We apologise for any offence caused and have requested the immediate removal of the competition."