A sudden, unexpected tackle.
Usually in parking lots, bed rooms, parties, or near pools.
sometimes a bird dog is a friendly tackle, other times meant to do harm.
The most famous bird dog is performed in the movie "Old School" by Will Ferrell when he bird dogs a man into a fountain.. this is where the term originated.
After Bridgett stole Steve's seat, he was forced to Bird Dog her in order to get it back.