The act of applying to a prestigious university with a low acceptance rate (such as Harvard or Yale) without additionally applying to a designated "safety school" or having a back-up plan in case the chosen school does not accept the applicant-- similarly to the Hail Mary play in football.
"So what schools are you applying to?"
- "Just Princeton, yolo man..."
"What about your safety school man, that place has like a 10% acceptance rate!"
- "Nah man, I'm pulling a Yale Mary!"