If someone asks me "What is that thing?", I usually reply with "It's an ENDS". (A term that someone here used a while back. Electronic Nicotine Delivery System) Sometimes I'll use ANDS instead (A for alternative). When they say "What?", I'll respond "It's a PV (portable or personal vaporizer)". When they say "Oh.." with a smirk usually, I'll say "No, it's an e-cig", and they'll usually say "Oh.", rather abruptly. At this point I can tell if they're interested in the thing, and the whole idea in general. Or if I want to spend any more time trying to tell them about it..