When swearing at somebody behind their back,
Then when they turn around to look at you, pretending to do something else with your hands; such as scratching your face.

The very first person to do a schafernaker, was Thomas Schafernaker; BBC weatherman.

Whilst making rude gestures to the news reporter, camera flicks to him live, as soon as he realises he is on air, pulls an amazing schafernaker!!
I told Bob to stop messing around and do his work! When I turned round he Schafernaker'd me!!
by BigWill88 June 6, 2012
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A cult scale that some British gay men use to assess the cuteness or 'hotness' of a potentially attractive man in their presence. It runs from zero to ten.

The scale is named after gay sex-symbol, the Polish-born BBC meteorologist Tomasz Schafernaker. The scale his named after him, since his cuteness is commonly considered to be beyond 10.
"Brad Pitt gets a 10 on the Schafernaker scale from me"
"You're not wrong there... whereas Gordon Brown or John McCririck would get 0 from me"
by Roger Mellie 84 October 9, 2009
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