The button you wish you had when you just sent that sexy text or pic-text to your lover--And then frantically look back at your phone to discover the horror--You accidently sent it to your Grandma!

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.