At least to me, team player means someone who is able to get along well with their team mates in a professional setting. On a personal setting, I don't care if they are friends or not, but it does help. Someone who is willing to help and contribute to the greater team objective. Doesn't think or work in a silo mindset or be super calculative on 'I did this and you did that'.

This does not mean I expect the person to just take on whatever extra work his teammates can not.

Honestly it just really depends on your boss and what kind of environment they were brought up in.

Interestingly, I've been reading the book "Quiet" by Susan Cain recently, and I do find her explanation on how traits like "team player" and communication/collaboration became so engrained in the corporate world - even in jobs and settings where such social interactions aren't essential - quite plausible. She calls this as an obsession with the "extraversion ideal", and how this could become a problem in the working world.

It’s just a cliché, don’t worry about it. They have to write something, and as it’s hard to write a good job description, they write stupid things like this.