A word of wisdom is a supernatural insight into the way to live well. Usually, words of wisdom come when there is a seemingly impossible situation (or one in which all the apparent solutions are bad), and then the Lord provides understanding of a way that had not been seen before.
Words of wisdom can occur out of a time of intense prayer and fasting or they can emerge out of casual conversation. When I receive words of wisdom, I usually am just talking with a person about their problem and I say something without thinking much about what I’m saying. Right after I speak, I’ll think, “Wow! That was a great insight. I should write down what I just said, since I’m not sure I can think of it again.”
A key difference between earthly wisdom we possess and a word of wisdom is that we should be able to repeat, apply, and expand our store of earthly wisdom. That’s what the whole book of Proverbs is about: learn these things, apply them to your life, and pass them on to your children. Words of wisdom are ephemeral. They are relevant in a powerful way to the immediate situation, but they do not belong to our set of knowledge. If we do not take care to note the word of wisdom and what might be learned from it, the revelation will pass from us.