Most probably they meant competing against another human player, probably online as mentioned above, or an overly competitive person.
I tend to be competitive, but mainly against myself. If a game has challenges I don't stop doing them until I have the highest time/score I can get. If I go online, and see that someone is playing the same game as me and got a higher time/score than I did, I will repeat the challenges until I get a higher number than that person. This happened with TMNT for the PS2. It has 16 challenges, and one day I decided to check the game on GameFAQs, went to the message boards and saw that someone had posted his times/scores for the challenges. His numbers were higher than mine in some, so I redid the challenges until I got higher numbers than him, which I did.
In sober doses, competition is good. As someone I knew from another forum used say: it avoids stagnancy.
Fair play is a rare thing these days, though.