nicotine
//ˈnɪkətiːn//
Noun
1
A toxic, colorless or yellowish oily liquid alkaloid found in tobacco leaves, which acts as a stimulant and is highly addictive.
Nicotine is the addictive substance found in cigarettes.
2
The addictive substance in cigarettes and other tobacco products that causes physical dependence.
Nicotine is the substance that makes it so hard to quit smoking.