A LSD Trip is when you take LSD and 'trip'. When somebody says they are tripping, this means that they're hallucinating. If it's a good trip, the person will spend most of his/her time watching colors fly around them while laughing or looking amazed. If it's a bad trip, the person could be filled with fear and anxiety. It's amazing how a trip can go from good, to bad, and even back to good very suddenly.
Guy 1: Dude, that was a crazy LSD trip we went on last night
Guy 2: Hell yeah, after it hit me, I don't even remember moving from my bed until after it finished peaking.
Guy 1: Hell yeah, we should go on a shroom trip next time.