renditions?

“The agency [CIA] was the pointy end of the spear,” said former director Mike Hayden, “I can’t confirm or deny anything the government hasn’t confirmed or denied. But we played many roles. We had certainly done detentions and interrogations. . . . We’d done renditions. . . . And that started within a year of the attack. And then later, after you get [long-term Guantanamo detainee] Abu Zubaydah about a year later, you get enhanced interrogation techniques.”

In this paragraph, what does "renditions" mean?