n.
1.someone who is so ardently devoted to something that it resembles an addiction
2.someone who is physiologically dependent on a substance addict v.
1.to cause (someone or oneself) to become dependent (on something, especially a narcotic drug)
Idiom of the Day
lose one's train of thought
to forget what one was talking or thinking about
I lost my train of thought when I was talking on the telephone to my friend.