Drad (or dradest) was a term that was used as both an adjective and an exclamation. As an adjective it often meant "best" or "wildest", while as an exclamation it leaned more toward "wild."
When talking about the Gathering, Chiana told Aeryn Sun that Molnon had said that it was the dradest and that it would blow her mind. At the Gathering, Molnon told Chiana that she should "take the stone" because it was the second dradest time, the dradest being the kiss they shared moments later. Molnon later told John Crichton that Chiana was going to "take the stone", and that it was going to be drad. ("Taking the Stone")
When Crichton and Chiana were in a transport pod outside of Moya, Chiana convinced him to take part in a simulation game. Once Crichton was inside and had encountered Scorpius, Chiana said to him, "drad, huh? Bring back memories?" After they both managed to escape the game alive, she said, "hey, hey. We're not dead. How drad is that!" ("John Quixote")