Snowflake (slang) is a 2010s derogatory slang term for a person, implying that they have an inflated sense of uniqueness, an unwarranted sense of entitlement, or are over-emotional, easily offended, and unable to deal with opposing opinions.

It's an insult. Background: at sometime in US culture (I don't know about other English speaking countries), teachers (and other adults) started telling kids that they shouldn't bully other children because they were "different." The message was supposed to be that everyone was different in some way - and also if you felt different than the other students, that was ok, because those differences didn't make you a worthless, waste of a person. Often times, the comparison would be made to snowflakes (because supposedly no two snowflakes are identical, no two people are exactly identical). "Snowflake" is making fun of that lesson - often by people who like bullying others for being different.

It's used to identify people who try to shut down free speech by pretending to be offended by any opinion different from their own. They are so fragile that they would quickly melt if they ever had to face real life. They cast themselves as victims so that they cannot be criticized. They can attack others but can't be criticized themselves because of their self-proclaimed victim status. If they can shut down free expression of opposing opinions then they can win the argument without any logical explanation for their own opinions. The phony story of bullying is just typical of their tactics. It's actually the snowflakes who are doing the bullying, of anyone with a differing opinion.

It's derived from a piece of dialog in a 1999 movie called "Fight Club." I've never seen it. Apparently it has a cult following. In the late 1880s, a man known as "Snowflake Bentley" developed a technique for making beautiful photomicrographs of snowflakes. He made hundreds of photographs of snowflakes. No two were alike. This led to the idea that "no two snowflakes are alike." Therefore, snowflakes have come to symbolize uniqueness and individualism. In the movie, a man tells a group of men, "Listen up, maggots. You are not special. You are not a beautiful or unique snowflake. You're the same decaying organic matter as everything else." The derogatory term refers to people who believe that they (and everyone) are unique, special, and entitled to respect. They believe they are "snowflakes." So, it means "people who think of themselves as 'snowflakes' but don't deserve it." Snowflakes are also fragile and delicate, so as an insult it also carries a connotation of people being weak or effete, not "tough." Incidentally, I believe first in the 1990s, researchers found that the shapes of snowflakes are the direct result of the sequence of temperature and humidity changes they experience as they fall through cold air, and that snowflakes that fall together are visually identical. They have published photographs of pairs of snowflakes that look identical. A Google Images search on "photo of identical snowflakes" will turn up many of them.

Sorry - accidental duplicate.