Verb that expresses the concept that the act of talking about a phenomenon changes the phenomenon. For example, if you see a squirrel come within 5 feet of where you are sitting, and you attempt to alert your companions, the act of alerting them will scare off the squirrel.
Taken from Heisenberg's Uncertainty Principle, which holds that it is not possible to know with certainty both the position and the momentum of a particle. The act of measuring either variable changes the other.
Dude, I would have shown you the squirrel, but I was afraid that I would have heisenberged it.