What the heck do these terms mean?

The solution of to how to best describe sound in writing is simple.
Don't try.

The only way it should be done is via A/B employing your ears.

In other words, do the reviews on Youtube with audio
actually demonstrating the point a reviewer is trying to make.
Now you say the audio quality sucks on a laptop. 
You could still discern differences between wet and dry,
fat and skinny, Polite and forward. 

Using the written form to describe audible differences is 
not going to work. People will simply read the material and
then make an interpretation that seems correct.
Highly inaccurate methodology it seems to me.
 
Admittedly this might abbreviate most written reviews by 80%
but hey it is our time they are wasting.

Ozzy welcome to the world of audiophiles.
Thank you for showing us the Emperors New Clothes! 

Let's hope this economic shakedown brings a sobering reality
long needed back to audio.

A transistor radio can sound great if the song moves you but it won't inspire you to pen an ode to the sound. Don't be jealous of someone who can put to pen what he feels in his soul. He's just trying to relate, not impress.

All the best,
Nonoise

Listening to "So".... Tony Levin’s bass lines have always sounded what I refer to as "liquid".

+1 @nonoise

Without good desriptive terms, I guess we're left with ( good, great, bad?) 

Frankly, the terminology and descriptions don't put me off all that much.  It may help some when the reviewer refers to a particular artists' recording, perhaps the portion of such that tweaked a comment...

But then, one has to duplicate same if possible to determine WTH they're referring To....

At that point, go listen for yourself with Your selection(s).
That's what you live with.

"This is the best 'X' I've listened to since...."

At home, sounds like 2 cats over a clothesline.
Go figure....