I've always heard it called a French Inhale. It's pretty easy to do once you get it right. It fucks you up a lot because it gives the smoke and THC a straight shot into your brain. Great fun. Anywho, take a hit but don't inhale after your hit, so the smoke is sort of still in your mouth. Curl your mouth upwards and move your tongue towards your teeth, and slowly bring air and smoke in through your nose. Practice with cigarettes. It looks cool as fuck if you do it right.