But what CarolC's cookie monster said was sensible enough. Words are what people say, dictionaries are just lists of words with definitions that help you check up on what they mean, and whatbthey have meant. And dictionaries are never going to be able to keep up to date with a changing language.

The only circumstances in which it is appropriate to treat a dictionary as a complete list of all the words you are allowed to use is when you are playing word-games like Scrabble or Countdown.