In the real world, it is a crystalline structure formed when water vapor molecules combine in temperatures below the freezing point of water. Scientists tell us that there are no two of them alike, and all of them return to that state of liquid water when subjected to temperatures above the freezing point of water.
When used to describe people, it is increasingly used as a derogatory term to define those who have inadequate skills to handle any concept that is not in total agreement with their distorted perception of the world. Or, more simply, those who become "offended" by concepts that most of us learn to handle before we are out of kindergarten. A snowflake has been raised by their parents in ways that give them an over-inflated sense of their own uniqueness, ignoring the truism of "you ARE unique . . . . . just like everyone else".
As insults go, it's hard to think of one that so clearly conveys so many flaws at once: Fragility, an ill defined yet pompous self-importance, weakness and immense self-delusion. If being called a snowflake offends you, well, of course it does. You ARE a snowflake. It's the stuff of self-help books, inspirational posters and elementary school assurances. The imagery before negation is lovely; we are each unique snowflakes, each worth treasuring because each of us is uniquely beautiful. Ignoring the fact that SOMEONE has to work.
The problem seems to be when these snowflakes congregate in places that are commonly referred to as colleges and universities where tax payer money is used to develop/maintain the facilities. The tuition and fees paid, usually by the parents, but increasingly by the sports budget, are used more to enhance the football team or the basketball team, etc. than to enhance the actual educational capabilities of said college or university. Thus the snowflake runs to their "safe space" to play with stress toys and coloring books when "triggered" by various innocuous micro aggressions.
Where once the college/university was a bastion of free speech and open mindedness, well known for robust debate, it has become instead a place for athletes and snowflakes. Think about it, how many jobs are available for those with advanced degrees in underwater basket weaving, or sports studies? These individuals think they are just as "unique" as snowflakes, when in reality, it is that their feelings that are just as fragile.
In my opinion, it is the individual that, due to laziness or total lack of mental or physical prowess, is unable to "qualify" for any college or university yet then DEMANDS the same level of "do-nothing-ness" of many/most snowflakes, that creates many of our problems. When they can not find someone, anyone, to financially support them, will and do look for snowflakes to raise an issue, ANY issue, and then use that as their excuse to riot/rob/steal.
While none can condone murder, I would really like to see at least a partial return to techniques of the late 1940s or early 1950s. During those times a bucket of hot tar and a sack of feathers cured many of their misconceptions. Of those that were not "educated" by the tar and feathers, were there not many that quietly "disappeared"?