Informal.
1. abrupt and complete withdrawal from the use of an addictive substance, as a narcotic drug, alcohol, or tobacco.
2. go cold turkey ,
a. to stop using an addictive substance abruptly and completely.
b. to undergo sudden and complete withdrawal from a habitual activity or behavior pattern.
c. to begin or do something without planning, preparation, or practice.
[ 1915-20, Amer.; prob. from the phrase to talk cold turkey to speak bluntly about something unpleasant, var. of TO TALK TURKEY; see TURKEY ]