So, I received some first-hand experience with a fellow knife aficionado about HK (not China) knife carry. and he pointed me to a Strider/Benchmade/Chris Reeve/misc knife dealer in the city. Things are looking up. I might just take a medium SAK, and see if I can snag a strider as a souvenir.
It's a hairy, ambiguous term. Loosely defined, it's a knife that can be opened with the use of inertia, or just the force of gravity (i.e., falling open when turned upside down). Most folding knives can potentially fit in that category, as they can be opened by "flicking" them with a little practice.
Organizations like Knife Rights have been fighting against "gravity knife" legislation in the US for a while now. A lot of people that carry folding knives don't even realize they can be opened in a such a manner, so they periodically found themselves running afoul of local laws without realizing it.
"Sapiens dicit: 'Ignoscere divinum est, sed noli pretium plenum pro pizza sero allata solvere.'" - Michelangelo
Technically a knife whose blade deploys solely by the force of gravity, i.e.:
But "legally" the term has been applied to lots of actual non-gravity knives. NYC holds that any knife which can be "flicked" open by holding the handle (or blade) and flicking the wrist is a "gravity" knife. Texas used to consider butterfly/balisong knives as "gravity" knives, but since amending their legal definitions, there has been judicial clarification. Several states consider butterfly knives, gravity knives, and automatic knives to all be of a kind and often lump them in together, treating the term "gravity knife" to effectively mean "scary looking folding knives".