This may sound dumb but I really don't know what it means and wanna know. I got a Transformers comic in one of those comic bags and it has a sticker on it saying 3rd print and then the price. What does 3rd print mean with comics?

It's not the original printing of the comic... in this case it's the third printing run of that comic.

more specifically, sometimes the innitial run of a comic book will completely sell out. If there is still demand there will be a second printing the following month. This can continue ad nauseum.

True, but anymore they'll go to trade paperback after a third printing. I don't think I've seen a 4th since WWHulk.

It's also be a recent trend to reprint multiple issues together, like Ultimates 3 #1-3 being reprinted in one book before issue 4 came out, or Guardians of the Galaxy 1 and 2 being reprinted together.