What is morphling?

Morphling is a type of pain killer used in the capitol. In Catching Fire, 2 victors from anterior games are addicted to this powerful pain killer.

Drug/painkiller. It's what we today call morphine.

It's like the insane pain killer. But if tu take to much then you'll become one of the 'morphlings' who competed against Katniss and Peeta in Catching Fire.

it's a drug, probably like morphine.