It means that you have a dirty little secret that you're not comfortable discussing here.

"giant black giantess" was what gave it away, I assume you were originally going to say "giant black girl", but then thought, "I don't want to use the term 'giant' to describe a female," and you really wanted to throw the word "giantess" in, so you did, but you accidentally forgot to get rid of the word "giant".

Hey OP, you should play Shrink 'High. I think you'd enjoy it. Heh heh.