Interj. When one sees a great pair of bazambas / bewbs / mamaries and / or amazing cleavage. Also, a nipple slip. Best said with pirate noises, ie "Rrrrarrrrr!" or "Treaaaaasure!"
Friend 1: Dude, have you seen Nicoline in that itty bitty red top today?
Friend 2: Tits ahoy, bro! Treaaaaasure! *high fives Friend 1*