Dan Loeb clearly wants to tell rival billionaire Bill Ackman where to stick it.

Yesterday, Loeb took a swipe at Ackman, whose massive $1 billion Herbalife short has been underwater for the past seven trading days as shares have surged.

“New HLF Product: The Herbalife Enema administered by Uncle Carl,” Loeb wrote as his Bloomberg message header, a reference to activist investor Carl Icahn, who has taken a 16 percent stake in Herbalife opposite arch-nemesis Ackman.

Herbalife has been on a tear since Icahn spoke at an investment conference last week, where he, too, poked fun at Ackman. Loeb was the first big name to oppose Ackman on Herbalife, but he sold his shares in February.

Loeb is renowned for his acerbic comments, but in recent years he has been trying to change his image. After the “enema” message was widely reported, he replaced it with something nicer: “Always take the high road.”