A person who is your best friend for almost two years and then after winter break they change into a complete and utter B**CH. You have a crush on them and they have a crush on you too. You finally actually tell them and they ghost you. You ask them to a dance and they say that they're not available on that day. You are in class together for both of those two years. You have so many inside jokes about a kid who moved and was rude to you and him. You give him your number and he just ghosts you even more. And then you moved and he changed so much and you don't have a crush on the current him but still have a crush on the old him.

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.