Hi Jens,
Yesterday i have found the following definition of Chakram in a certain glossary:
chakra sharp-edged metal disc used as a projectile weapon by medieval and early modern yogis; also yogic term for each of the seven centers of energy in the human body; from Sanskrit chakram (wheel).
This is the link.
http://www.cambridge.org/catalogue/c...1851688&ss=fro
All the best
Fernando