Cold turkey refers to the clammy, cold, sweaty and goose bumped state of the heroin addict that is trying to "kick" the habit. This happens when the junkie decides to give up heroin without any sort of support mechanism - such as methadone - to take the place of the heroin. The body reacts by turning cold, clammy, sweaty, and the skin resembles that of a cold turkey.
"Did you hear Jojo was giving up junk?"
"He's going cold turkey - he looks like hell."