A doctoral degree pursued solely for the status conferred by the title of "Dr." and the lifestyle perks associated with living in a desirable location, without any genuine interest in academic achievement or contributing to a field of study. The motivation for obtaining a "vanity PhD" is entirely based on the superficial benefits of holding a doctorate (social prestige and lifestyle) rather than the pursuit of knowledge or a passion for research.
"Did you hear that Catherine got into Columbia University for a PhD in biostatistics? I was surprised considering she wasn't particularly adept at statistics in her undergrad."
"I wouldn't shower her with too much praise, it's nothing but a vanity PhD – she just wants to be known as 'Dr. Caldwell' and explicitly said she didn't want to do her PhD at Penn because 'she couldn't imagine spending her twenties in Philadelphia.'"
"Oh wow, so she's not doing a PhD out of any regard for pursuing the higher truths of academia or for the love of learning. It's all just to fluff up her ego and drink and party in New York City. A vanity PhD if I've ever seen one!"