Dark and laid back vs bright and forward

What do reviewers mean when they describe an amp as dark? Laid back? Forward? Bright?
Subjective meanings - bright or warm better describe sound to me. Forward and laid back just don't describe timbral or tonal variation to me.

Initially when I started reading Stereophile in the early 90's, I thought forward and laid-back described soundstages that projected from in front of or behind the speakers.
I've come to accept something more like Mshan's definition of forward and laid-back
According to J. Gordon Holt, "The Audio Glossary", 1990
(I hope the critics all read this so that we are all on the some page ;-)!

Bright/Brilliant: Describe the degree to which reproduced sound has a hard steely edge to it. Brightness relates to the amount or energy content in the 4- to 8- kHz band. It is not relating to output in the extreme high-end range.

Forward: A quality of reproduction which seems to place sound sources closer than they were recorded.

Dark: A warm, mellow, overly rich quality in reproduced sound.

Laid-back: Recessed, distant-sounding.
Just spotted a great memories of Patrick(Lugnut) may God rest his soul in great piece.