A system that emphasizes the details of music loosing midrange emphasis as well as rhythm and pace (think musicality / the emotional connection). So the tick of a drumstick against the cymbal is highlighted but voices are typically subdued. Typically a trait of older and less expensive solid state (not tubed) audio gear.
High end audio for those that care to pursue it has a very large vocabulary. It takes a lot of exposure to music and to the nomenclature to learn and connect the two. If you are interested, I recommend Robert Harley’s book The Complete Guide to High end Audio. This is an excellent place to start and a reference to reread occasionally.