A marijuana smoker who smokes in Private, secret places, often perfecting skills to avoid getting caught or letting on to others that the individual is lighting up. Often a life style always looking for the next opportunity to toke. Often it is more so the thrill of sneaking a toke in than it is to get blazed, as a ninja smoker often tokes just enough to buzz.
pothead "dude i had no place to smoke last night"
ninja smoker "i ninja smoke in my mom's basement when i need a quick toke"