In this context, it's matters related to government, politicians, or the general culture of a country, in which there are two or more major camps of conflicting opinions, where a good deal of people in one or more of those camps view the other camp as evil because of their view.
If the post is in a community where only one of the camps is significantly present, but the post is attacking the other camp, it is still political.
Why do you ask? Are you hoping to expose some inconsistency in my definition? Maybe use it to call something I like political with the expectation that I'll disagree with you? Or were you expecting my definition to be biased, calling something political that shouldn't be, so that you could expose me as a moustache-twirling villain?
Not upset, just suspicious because I've seen you asking that question a lot.
Obviously what I consider political is up to my discretion, but I'm pretty sure the general definition does not include contentious memes, and mine doesn't either because I gave a clause about one side considering the other side evil because of it.
In general, if a person asks themselves "is what I'm posting political?" they can answer correctly 95% of the time, and the 5% of edge cases won't upset 95% of the complainers.