Bright: Emphasis on high-frequencies, specifically upper-mids with emphasis on harmonics.
Crunchy: Exists between 2K and 4K, typically distortion based and generally pleasant. Can lend rhythmic distinction to distorted rhythm parts.
Detailed: Minutiae of the music are easily audible. Present sounding, intimate and close with lots of articulation and transient response throughout the upper mid range.
Forward: Present, in your face. Detail present in transients and upper harmonics which lends a feeling of proximity.
Glassy: Brittle sounding, too much upper-mid content especially with regard to harmonics in relation to fundamentals.
Grungy: Lots of distortion with emphasis on odd harmonics.
Hard: Excellent transient response combined with an overemphasis on upper-midrange frequencies.
Harsh: Peaking in the 2-6 KHz range.
Metallic: Emphasis on upper-mid range frequencies, specifically those that deal with odd order harmonics in this range.
Pinched: Narrow-bandwidth, often relegated to the upper-mid range frequencies. Try boosting lower frequencies to balance.