1. "Hint hint" is something that someone says sarcastically to another person to guide them into the correct direction, to let them know that they are close to a solution (usually by pointing their finger to the correct area, etc...), it is simply dropping a 'hint" to an otherwise temporarily or permanently clueless person.
EX: This Blonde Bombshell was hitting on John, but he was so nervous that he could not reply with anything else other than a nod. I think the cat had his tongue LOL! So I whispered: "Hint hint" *elbow jab* John! get on the ball or I will. Well, John wussed out and I had a sweet one night stand with a total babe! I think John put her on his MILF list. Ooooooooooh she is SO fine! I won't tell John that she gave me her number. I am gunna ring her soon too; she told me to give her a booty call anytime!
"Hint, hint" is what you say when you're trying to get someone to do something or realise what you're asking them for, when it would be rude or inappropriate to ask them to do it directly.
It is said humorously to make it a bit more obvious that you're giving hints as to what you'd like them to.
Brother: My friend is coming round tonight, and we're hoping to have a little bit of time alone together, hint hint, if you get my drift, hint hint.
Sister: OK OK, I get it, I'll get out of here.
Girl: Mmm, I think one of those engagement rings would look really good on me, don't ya think (hint hint)?
Guy: Hey, look at that... thing over there!