Its generally a category.
The only real distinction is with workstation cards, as those are vastly different in use that "gaming" cards.
I typically break it down into 4 levels (Basic:Usually the same as an iGPU. Entry Level: Cheap cards, easy upgrades (ie 750Ti). Mainstream: Good enough to run just about anything, not the best for maxed out or higher resolutions. Flagship: Best of the best)
I never really use the term Enthusiast Grade, but I would consider it mainstream or flagship levels of performance.