What does being behind the black ball means?

Answer:
This is a billiard term that has been co-opted as a general term. In the billiard game of 8 ball, there are 15 balls on the table. The object is to get all of your balls in a pocket, either 1-7 often refered to stripes or 9-15 refered to as solids and then sink the 8 ball. If you accidentally make the 8 ball before you make all of the others, you lose. So, being behind the 8 ball, which is black, is an unenviable position to be in.
First answer by Napalmcheng. Last edit by Napalmcheng. Contributor trust: 18 [recommend contributor recommended]. Question popularity: 1 [recommend question].