Good Glass or Good Lens?

One of my readers asked me: What do you mean with ‘good glass’?
I am sorry for my photographer’s lingo. A lens which is sharp and has good colour rendition is called ‘good glass’. 
Lenses with bad sharpness or bad bokeh are called ‘lenses’ or just ‘bad lens’. See and hear what Scott kelby has to say on lens terminology in this video (topic starts 4:36 minutes into the video, ‘glass’ is at 5:45 minutes ).

Scott Kelby has made an informative series on lenses. Too bad he is Nikon oriented (-:.
The first part starts here. The other parts can be found here (go to season 1).