Refers to when a person becomes obsessed or/and overwhelmed by a sport they have joined to the point where they have no free time or/and they lose interest in their friends or other hobbies.
Not to be confused with dedication to the sport or an over-zealous sports fan.
Anton: So can you go to the movies this weekend?
Jessica: No, I can't. I've got soccer pracitce.
Anton: That sucks. How about next week?
Jessica: No, I have practice then too. A big game is coming up and I can't afford not to go.
Anton: Geez, you haven't been out in forever. Talk about a heavy case of jock-cancer.