Those who take the dictionary to be word-perfect should take the time to look a little harder.

It has taken the keen eye of a Queensland University of Technology physicist to spot a 99-year-old mistake in the Oxford English Dictionary.

Queensland University of Technology physicist Dr Stephen Hughes.

The error may be slight, but it's an error nonetheless, Stephen Hughes said.

Dr Hughes claims he has discovered that the dictionary's definition of the word "siphon" has been incorrect since 1911.