Reference

Acoustical absorption
Good: adequate, appropriate, "good acoustics," unobtrusive
Not Good:
    Excess: dead, dry
    Deficiency: billowy, echoic, fluttery, live, plastery, reverberant, slap

Audibility (of flaws)
From best to worst: Inaudible, subtle, slight, moderate, significant, conspicuous, severe, extreme, intolerable, or Aaagghh! (screaming-up-the-walls)

Detail
Good: accurate, crisp, delicate, focus, resolution, snap
Not Good:
    Excess: accurate (misused), analytical, clinical, etched
    Deficiency: closed-in, congestion, diffuse, hangover, haze, opaque, smearing, veiling, velvet fog

Distance
Good: Program-dependent
Not Good:
    Close: aggressive, forward, row-A, up-front
    Distant: laid-back, recessed, row-M

Frequency response
The following terms describe how a system's or component's frequency response sounds, not necessarily how it measures. Phase shift and distortion can sound like frequency-response aberrations.

ENTIRE RANGE
Good: airy, accurate, alive, balanced, extension, flat, neutral, smooth, uncolored, weighty
Not Good: dark, chocolatey, discontinuous, light, lumpy, syrupy, tilted, treacly

BASS
Amount
Good: balanced, full, natural
Not Good:
    Excess: boomy, dark, fat, heavy, rich, syrupy, thick, tubby, warm
    Deficiency: cold, constricted, cool, lean, overdamped, pinched, sparse, thin
Smoothness:
Good: natural, smooth, tight
Not Good: boomy, lean, lumpy, one-note bass, thin, tubby, uneven, woolly
Extension (frequency range):
Good: deep, extended, foundation, infra-bass, seismic
Not Good: pinched, restricted, shallow, sparse, thin

MIDRANGE
Good: alive, jump factor, natural, neutral, realism, uncolored
Not Good:
    Excess: aggressive, brassy, close-up, forward, humped, projected, row-A
    Deficiency: dished, distant, laid-back, polite, recessed, reticent, withdrawn
    Colorations: boxy, chesty, honky, hooty, horn sound, nasal, raucous, vowel ("a," "ah," "aw," "ee," "eh," "ih," "oh," "oo," "unh")