A snowflake is someone who advertises that they are special and unique and therefore deserves special and unique treatment or consideration. Every snowflake is special and unique and there are no two snowflakes that are the same, hence the term. The general behavior pattern for a snowflake consists of associating with the most obscure and marginalized identity group possible which they will milk for victim points.
Contrary to popular belief, 'snowflake' does not refer to someone who merely complains or gets triggered, though there is such significant overlap between these behaviors that the confusion is understandable. There must be some sort of reference to a 'you need to do what i say because i am _____' attitude for the term to properly apply.
average human college student: 'this lecture is triggering my trauma as a polysexual neurodivergent queer person and i demand that it not be allowed.'
normal people: 'not my problem, stop being such a snowflake and get over yourself.'