It used to mean something better than that - a "grinder" was someone in old-school parlance a "wirehead". That is, they were someone who uses or tries to use t

It used to mean something better than that - a "grinder" was someone in old-school parlance a "wirehead". That is, they were someone who uses or tries to use technical and/or electronic means to "hack" their brains, for stimulation, improvement (memory or other cognitive function), etc. A mild version would be something like using a tDCS system (especially if home-brewed). A hardcore version (I do not know of any real-world examples) would be some kind of homebrew brain implant. Note: Such individuals are not the same as those who implant things like magnets or id chips under their skin for various purposes - though there is overlap of the two communities. I'm not sure what - if anything - "grinders" call themselves today, or if there isn't any issue at all (part of me suspects the latter).