A Kellicam is a Klingon unit of length measurement.
Before decloaking to attack the Enterprise in orbit of the Genesis Planet, Commander Kruge waited until his target closed from 5.000 down to 500 kellicams. (Star Trek III: The Search for Spock)
Commander Klaa engaged his cloaking device 8,000 kellicams before reaching attack range, during his assault the Enterprise-A in orbit of Nimbus III. (Star Trek V: The Final Frontier)
The T'Karath Sanctuary is located roughly 37 kellicams south of Mount Seleya. (TNG: "Gambit, Part II")
Klingon transporter systems have a range of 20,000 kellicams. (TNG: "Redemption")
While searching along the Cardassian border for the IKS B'Moth, General Martok wanted the IKS Rotarran to maintain a distance of at least 5,000,000 kellicams from the border. When the B'Moth was finally located, it was discovered adrift 500,000 kellicams inside Cardassian territory. (DS9: "Soldiers of the Empire")
It was stated in "A Matter Of Honor" that Federation transporters have a range of 40,000 kilometers. If Klingon transporters have a similar range, this would indicate that 1 kellicam is approximately equal to 2 kilometers. This is the measurement given by the Star Trek Encyclopedia.