If you check it out (dictionary, thefreedictionary, define), dictionaries focus on the emotion of happiness and experience of pleasure, and perhaps their causes, as the key elements of joy. The fact that these are involved is obvious; but I don’t think that our Christian joy is limited to this. I posit that real joy is something deeper, that clearly can encompass these ideas, but goes further:
Happiness and pleasure can be signs of joy, but at any given moment, one does not necessarily have to be feeling happy or experiencing pleasure in order to be joy-filled. Furthermore, at any given moment, if one is happy or experiencing pleasure it does not necessarily follow that one is joy-filled.
I will deal with the second half of this first, as it is somewhat more concise and obvious.
Let us imagine that there is some person who does not have this constant, enduring, Biblical joy. This is quite easy- we know plenty of people without it. It is no stretch of the imagination that some event or experience – perhaps being given a gift, or a massage, or doing any activity they enjoy – gives them pleasure. We ourselves have seen it. Similarly, this person may feel happy for a short time, but when that time has ended they return to this joyless state. Again, we know this happens. The dictionary may say that they experienced joy, but they’re using a different definition. We can see that although someone may, even frequently, experience pleasure and feel happy, this does not mean necessarily that they are joy-filled.