You start the game while you are having any conversation with someone. Pick a word that the other victim or victims are saying a lot. Secretly discard the meaning of that word for that of another secret word, and continue with the conversation without saying your secret word. Here's an example:
 

Victim: Hi, do you have Jesus in your life? (The player mentally applies the meaning of the word "CheezWiz" to the word "Jesus".)  Player: Well, occasionally. I mean, I don't have any Jesus right now. Why do you ask? Victim: You mean you only think of Jesus and how he died for you while you're in church? Player: No, I mean sometimes I've had the urge to get some Jesus while I was at the grocery store, but usually I pass it up there. Mostly I'm tempted by Jesus at parties. You know, if Jesus happens to be at a party I might grab some and stick it on a cracker.  Victim: What? Player: But mostly it's not for the taste of Jesus, it's for the aesthetics. I'm real good at making what I call a "Brain on a Ritz". That's when you carefully arrange Jesus on a cracker so that it looks like a miniature brain... Victim: ?!?!?

And so on. Now here's how you win or lose:

You lose if you accidentally say the secret word whose definition you are using in place of the spoken word (in the previous example that word would be "CheezWiz"; if the player said "CheezWiz" instead of "Jesus" the player would lose).

You win if your victim says the secret word. So in the previous example, if the victim suddenly broke in with, "Hey, you're talking about CheezWiz!" you could congratulate him or her on a game well played, say "better luck next time" or something like that, and continue on your merry way.

Now, to clarify, you don't have to use "CheezWiz" as a secret word. You can use "Spoon" or "Greenpeace" or whatever comes to mind. Here is another fictitious example:
 

Victim: ...I mean, like, c'mon, oral sex is still sex, right? (Player quickly inserts the definition for "hygiene" into the word "sex".) Player: Sure, it's a subset, just like taking a shower or cleaning your ears.  Victim: Taking a shower is a subset of sex? Player: Duh! Why don't you look up the definition of sex before you use it? I guess taking a shower wouldn't be a type of sex if you took one without soap and used dirty water or something... Victim: I have no idea what you're talking about. I was just saying that everybody, including the president, knows that oral sex is sex. Player: Why are you so obsessed with sex? Do I smell bad? Victim: Leave me alone.

Here, the game seems to have ended in a draw, or perhaps it could be continued later.

Enjoy your 'Wizzing!  Send transcripts or any fun CheezWiz anecdotes my way.