There are two types of power hits:
When there is a group in a session usually when there isn't much weed. 1 person usually the male will hit the blunt(or whatever they are smoking) and as he exhales he blows the smoke into the mouth of a female. This can be done with the same sex but usualyl with tubes that will transfer smoke instead of mouth to mouth.
Guy: Hey baby want a power hit?
Friend: that isn't fair you guys basically get 2 hits!
1. A spike or drop-out in the electricity supplying your machine; a power glitch.
2. To use a bucket method for smoking cannabis.
1. "Oh man! I was in the middle of the hardest level of Half Life 2 when my computer had a major power hit!"
2. "Dude, we were at Aaron's party yesterday and we did the most awesome power hit. I swear I was high off my rocker for the rest of the night."