According to Stereophile, here are some audio descriptor definitions:
dark - A warm, mellow, excessively rich quality in reproduced sound. The audible effect of a frequency response which is clockwise-tilted across the entire range, so that output diminishes with increasing frequency.

warm - The same as dark, but less tilted. A certain amount of warmth is a normal part of musical sound.

bright, brilliant - The most often misused terms in audio, these describe the degree to which reproduced sound has a hard, crisp edge to it. Brightness relates to the energy content in the 4kHz-8kHz band. It is not related to output in the extreme-high-frequency range. All live sound has brightness; it is a problem only when it is excessive.

harsh - Gratingly unpleasant to the ear.

detail - The subtlest, most delicate parts of the original sound, which are usually the first things lost by imperfect components. See "low-level detail." Compare "haze," "smearing," "veiling."

Hope that helps!

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Take Care,
merc