Jack smiles and says "pirate"
Ok I know a lot of people here probably wont agree with me..but I don't think Jack is smiling like that because she is behaving like a pirate by betraying him..the dude is smiling like that because he can clearly see that she loved what he tasted like.
Jack knows that Elizabeth is a pirate..because she has betrayed him to save her own life once before..and she seduced him to do it back then too..and he realized that she doesn't have feelings for him in that way(YET)..and she has betrayed lots of other people too in order to save her own life...and Jack knows it..
What he doesn't know...is if she actually wants him..and once she has had a taste of him..will she still want him?
Jack wants the woman its obvious..and not just for sex..so he is desperate to know if there is even a chance...
In the curiosity scene IMO, Jack is basically telling Liz that one day she wont be able to resist coming over to HIS side..to be with him..and she will act on selfish impulse..one day she wont be able to resist him as in she wont be able to resist tasting him..to see what HE'S LIKE
I know he doesn't literally say it but as T.Maria says..they are trying to not make the Jack/Liz thing too obvious too early on so its all bloody CRYPTIC talk..honestly this movie confuses us all so much because of all the symbolisms they use and not actual flat out obvious statements that these two friggin want each other and why? Cuz its only the middle of the over all story so they don't wanna give too much away in movie 2 IMO..and when movie 3 comes out and you watch movie 2..you will be like..."OH YEAH now I understand what he's really saying there!!" I bet you!
So yeah this scene totally isn't about him wanting her to be a pirate..because by movie 1 she has already proven to be one to him...he just wants to know if this woman wants him as a MAN..
and when you look at it this way it makes much more sense to the rest of the story in movie 2 because she is actually starting to find it hard to resist Jack Sparrow all of a sudden...she's in no way finding it hard to resist being a bloody pirate in this movie. She's quite obviously embracing the more free side to being a pirate in movie 2 without a worry because she is already a pirate at heart and she knows it..
When you look at what he's saying in that way about her resisting the temptation of issing him and how one day she will to see what it's like the end scene then makes a WHOLE LOT MORE sense because If betraying him like a pirate was the thing she was truly worried bout doing..and was resisting then..why did she find it so EASY to make the choice?.. I mean that look of pure determination on her face once she did it..betraying people is NOT hard for her..she's used to doing it to save herself....I kept asking myself why she looks as if she has no care in the world once locking him there and then all of a sudden you see her basically go weak in the knees.
IMO the betrayal wasn't the thing she was contemplating doing in that scene because its not in her nature to worry about betraying someone when HER life is in danger..she does it all the friggin time even to her friends..she's actually wondering if she should taste Jack or not before she does it..She could have used one of the guns to force him to stay there..she could have used her sword all whilst his back was turned...but NO..no no..she gives into the temptation of tasting Jack before she does it she decided to use that as a way to betray him..when she didn't have to..
So yes she kisses him and damn she gives him one heck of a good mouth wrestle because its the very thing she was tempted to try through out most of the movie..and she can make meal out of it if she wants to because she doesn't have to face the repercussions later cuz she is going to betray him either way..if she likes it or not..because during times of danger..as usual..she will put herself first no matter what. Jack has to die so she can live in her mind..thats the selfish thing about it..she's going to kiss him and leave him no matter what..despite the fact she knows he wants her..
So when she actually chains him there..Jack doesn't actually smile because she's betrayed him..she's done this to him before..she's used seductive techniques to betray him on the beach so he pretty much expects it..he smiles cuz this time she used a kiss ..and he quietly waits to see what her reaction will be..to see if she liked it..he sees that she's having trouble trying to stay focused on his eyes..because hers keep slipping back to his lips....he then sees if he can prompt her to kiss him again..he looks at her lips and this causes her to basically almost kiss him again..this is enough for Jack..he smiles with satisfaction and and says "pirate" with pride..and its not because she has just acted like one because she has done it before to him. Its because she loved that kiss and she wants more..its basically saying "you are MY pirate"(again the annoying cryptic crap)
And then look at Liz's reaction LOL..she realizes he was right about her..she would want to taste him one day..and when she did..she would LOVE it..her face says all "no i don't!" and Jack actually looks as if he is about to laugh at the denial..and his face says "yes you do!" and then she leaves