Like you try to start a conversation, about anything. It could be smalltalk, about events, happenings, or even voicing out your own thoughts about something, and people will barely look at you, shrug, or pretend you're not talking to them. This could be coworkers, family, or people you just run into at a social place.
You could have concerns about something at a workplace, and your coworkers will quietly look down at their phones in silence and not respond. Other types of people would just give a vacant expression and walk/run away from you without engaging in any conversation.
I used to think I was very anti-social growing up, I was a huge introvert, but now I see other people cowardly retreating into the corner of their own brains and blocking out reality that I realize that I really have no reason to be scared.