Apparently, the Oxford English Dictionary (OED as it’s called by some) has had a mistake in it for the last 99 years.
It’s incorrectly stated that a siphon works because of atmospheric pressure, but it turns out that’s just good old fashioned gravity.
To be fair, though, research has indicated that nearly every dictionary has contained the same mistake.
I think the mistake is perfectly understandable. I’m sure that the editors at dictionaries are far more interested in determining what new words to include (I wish they’d spend less time approving some of them…) than analyzing the scientific validity of a word that’s been around for a couple of centuries.