Note: "Rebound" is not exactly correct here. Mac Magic explains what the meaning of cold turkey is, but we use the word "relapse" as what someone does when they are trying to kick a substance habit but they go right back to it again. It's usually used when talking about taking drugs or a drinking problem, but can be used for smoking, overeating, etc. just not as much. A "rebound" is the word synonymously used when someone finds a new [romantic/sexual] partner rather immediately after breaking up with another. It is the partner not to be taken seriously as they are "on the rebound" from their last partner.

The expression in question is 'to quit cold turkey' which means to quit completely (instantly, not gradually). For example: "I quit caffeine cold turkey." Quitting cold turkey can shock the body, and make withdrawal symptoms worse. We call that 'rebound.'