1. a cigarette-shaped device containing a nicotine-based liquid that is vaporized and inhaled, used to simulate the experience of smoking tobacco.
"more smokers are turning to electronic cigarettes to help them quit smoking"
Whatever sporadic cigarette smoking that I've tried was done years ago, but when on Vacation, I admit to having the odd craving for a Camel, or some equally repugnant strong cigarette (one reason I should avoid Vegas!). This has led me to consider the whole E-cigarette fad, and whether that would be a good alternative to satisfy the occasional nicotine craving. The main component of these devices is electronically vaporized, liquid nicotine often combined with other chemicals or flavoring elements. Presumably there are fewer toxic chemicals in the vapor as compared to regular cigarettes, but the product is unregulated and has not been rigorously studied in terms of health outcomes. There's no second hand smoke, but second hand vapor may not be harmless either. It's hard to believe that there wouldn't be some adverse effect on the lungs by inhaling concentrated nicotine. Children may be at special risk, as nicotine may slow the growth of the adolescent brain.
So I suppose it's buyer beware at this point, and avoiding temptation seems like the best option - In Vegas or not.
Get more information on E-cigarettes at How Stuff Works: 10 facts about e-cigarettes.