A person who utilizes Youtube and Wikipedia in order to garner as much palatable information on subjects within the realm of physics as possible. Possibly for personal interest but more commonly used for 4 AM post-party diatribes about how we're all connected and the ancient shamans were right.
Most often using 'Quantum' physics for their purposes, as it is the most subjective branch and easy to bullshit the uneducated about.
Stephen: So you're interested in physics?
Dave: Yeah, a bit. I'm an Armchair Physicist.
I found Dave up again when I left for work this morning. He'd been watching something on Youtube and kept going on about how dark matter means we're all just in a computer simulation. That guy needs to get a job.