An amazing girl. She’s smart, funny, really pretty. Her personality is also incredible and she’s a perfect friend but people realize this later. You need to meet someone like her right now or your life will be really bored...

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.