What makes gamer a "gamer"?

Be definition, anyone who plays a game is a gamer of that game. Addiction to one or multiple games is a choice.

 

How much time one puts in for playing games

 

I think "gamer" will have different meanings for different people. The word itself can be confusing in certain context.

For instance, if you play sports (football, basketball, etc.), you are technically a gamer. But someone who plays video games might not think so, but that's because their mindset is more specific (they're talking about video games, not games in general). Yet, if sports isn't considered a game, then why are eSports considered games? Also, does calling eSports "electronic sports" even make any sense, since sports require physical activity?

And if you include people who play sports as "gamers", what do you call people that play chess, checkers, Solitaire, a Rubik's cube, etc.? Surely those people are gamers, too. Sometimes there's even competition (especially in chess and in Rubik's cube solving), so does competition make those people gamers?

And if it's the "act of playing" that creates a gamer, do people that "play" instruments count as gamers? If not, then what would you call people that use a piece of software like Synthesia, since that piece of software falls under "music video game"?

And what about other game genres? Learning games? Simulations? The list goes on...

Ultimately, it's hard to really define gamer, other than the broad definition of "someone who plays games".