Anything that's subpar is worse than average. When a football team has a subpar season, it is a huge letdown for their biggest fans.
Subpar things just aren't up to their usual standards. Your subpar attendance at school may mean extra homework, and the math team's subpar showing at the district competition might keep them out of the state finals this year. In golf, subpar means a golfer had to hit the ball more times than expected to get it in the hole. Subpar is from sub-, or "under" and par, or "average," from a Latin root meaning "equality."