I was going to start this post with the dictionary defintion of the word "entitled", but its usage as an adjective seems to be a neologism. Perhaps that shouldn't surprise me overly much, as entitlement as a negative term seems to have gotten more popular in recent years, albeit with some pushback. Being entitled, in common usage, has come to mean that you expect something for nothing and that you expect more than is reasonable. It has been used about the youth of today (I dare-say in every era), the recently unemployed, men embittered by gender relations, people in southern Europe, and just about any other group that another group doesn't like. The problem with the word is that it's a lazy way of slandering people without backing it up by saying the way in which they are entitled. To feel that you are entitled to something can, after all, both be good and bad, depending on what we think we are entitled to.
To begin with the good, people should feel that they are entitled to human and civic rights, a working education system and economic structure, equality under the law, a central bank concerned with a well-working economy for the masses rather than a small group of creditors, and in general decent opportunity in life. If we feel that we're entitled to these things, we will fight for them, and they are worth fighting for. To shrug away people's completely reasonable concerns and ambitions with the word "entitled" is to spit in the face of everyone who has fought for social progress and democracy throughout history.
On the negative side, we have people who think that they deserve something particular by virtue of who they are, rather than wanting something they think everyone deserves. Like men who get bitter at women for not giving them a good-night kiss after having paid for dinner or who think they deserve a date with the person they like and don't want to take no for an answer, or people who think that they should be treated differently by the law because they're such important individuals. Calling them out on their negative behaviour makes sense, but to use the term entitled without properly backing it up with what they're entitled to and thus why it's fucked up is to further lower the discourse (though admittedly, I have not seen too many examples of the latter).
The words entitled and entitlement should not be seen as bad in and of themselves, and should never be allowed to be used to avoid a discussion about the role of the state and what we collectively should reasonably expect of society, nor as a way to avoid saying outright why something a person is doing is bad. Or as I could also have put it, weasel words are bad.