Chelski means: The English football club Chelsea F.C. after its takeover by Russian oligarch Roman Abramovich; influenced by some Slavic surnames ending in -ski.. The word is mostly archaic or historical; you will only encounter it in old texts, period drama, or school history rather than current teen conversation. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. It is sporting vocabulary and harmless in itself.