A nonconformist is a person who does not conform to the trends of the average person. A true nonconformist does what they want to do and not what other people want them to do.
This is not to be confused with an anticonformist, which is a person who does the opposite of what the typical person does.
Anticonformists often call themselfs nonconformists, because they dont know any better.
At a party where the majority of people are drinking:
The conformist would drink till he/she can't drink no more.
The anticonformist would not drink a drop.
The nonconformist would drink as much as he/she feels like drinking.