A situation between 2 people where each is waiting for the other's task to finish, so nothing gets done. When you walk down a narrow hallway, and you go to one side so they can get by, then the other person goes to the other side, blocking you again...that is deadlock. Deadlock is also when you go shopping with your mom in a strip mall and you don't say where to meet each other, so you go looking in store A while your mom looks for you in store B, then you get the idea that she's looking in store B, so you go there at the same she decides to look in store A. Named after the computer processing term of the same name.
I always get deadlock when walking down the aisles at the convenience store, they are so narrow.