When describing tone, many guitar players use a myriad of terms to describe the sonic qualities they perceive  I want to take a closer look at some of those terms and try to explain what they mean. It is worth mentioning that most terms relate to ‘feel’; the feel a pickup gives you is crucial to the tone you perceive. I will attempt to describe some of the most and more often used tonal descriptions.
Aggressive – An aggressive tone is very energetic and forward. Everything you play seems to ‘hit’ you in the face vigorously. It has a lot of everything, too: lots of highs mids and lows, lots of output. The lows are generally very tight, the highs seem to have a lot of bite and cut to it and there’s a huge amount of midrange, designed to really push your amp to the edge.
Airy – Airy is a bit like flutey, but with less mids and even more articulation. Sits in between flutey and bright.
Articulation – Articulation is about how the notes are separated from each other. Some pickups show each note extremely clear, others are less defined. A very articulated tone is often quite bright and clean and can be flutey but is less likely to be creamy.
Attack – When every note starts very ‘sharp’ where ‘sharp’ has no relation to the pitch. Each note has a clearly defined, sharp, clear-cut start.
Bloom – This term is being used a lot with vintage styled pickups and means that the note ‘opens up’ (blooms, like a flower) when you hit the note. As if it gains a bit of power and volume after the initial pick.
Bright – Bright is the opposite of muffled and mushy: it has a lot of high end. Brightness doesn’t necessarily mean that the high end is harsh or biting, it just has a lot of it. Brightness can also mean that it’s very articulated (i.e.: clearly separated notes). Brightness and articulation can be used to mean the same thing.
Chunky – A powerful low end with a push in the lower mid range, giving you a solid feel.
Creamy – Creamy is usually used for the tone of neck pickups, but a bridge pickup can have that characteristic as well. It usually means that the notes flow together smoothly, without emphasis on the highs, but with a push in the mid range,  giving that fluid feel. It’s almost as if legato runs flow out of your fingers by themselves. It should not be confused with ‘muffled’, which means that the voice of the tone is muffled as if you’re speaking with your hand in front of your mouth. It’s just about the way the notes flow together.
Compressed – Little or no difference in output. The lower output levels are bumped and the peaks are lowered. A compressed feel makes it quite easy to do complicated techniques like tapping and artificial harmonics.
Cutting through the mix – The mix means the sound the entire band makes. Cutting through the mix means that your tone stands out in that mix, like that little speck of garlic in a stew. You don’t need a lot of it (in guitar-terms: volume) to stand out.
Djent – This refers to a heavily distorted guitar that is being palm muted with staccato playing and produces  a sound similar to dj-ent. It was coined and popularized by the metal band Meshuggah. Some people use this term to describe a style of music.
Fat – Fat is what happens just before the tone gets mushy. It has a lot of lows and lower mids but with enough clarity to not be swamped in the mix or in your own tone.
Floppy – A tone that’s overall not tight with a very loose, flexible feel.
Flutey – Flutey is a difficult term to describe. It often refers to the neck pickup and usually entails a specific kind of clarity. A flutey pickup stays clean, no matter how much distortion you dial in. It has a feel a bit like you’re blowing over the edge of a bottle; that’s the flutey thing going on! Joe Bonamassa has an amazing tone, and his neck pickup surely has that ‘flutey’ quality that’s being coveted by many players.
Growl – Some tones seem to have a lot of push in the lower mids, but retain a lot of their clarity. Growl perfectly describes that tone. It’s not really aggressive, it just growls, like a bear!
Juicy – Juicy is much like creamy, but a bit less thick. A creamy pickup can be a bit too unclear in some guitars, and a ‘juicy’ pickup will go a long way to be creamy, but has some ‘flutey’ qualities too.
Hot – If the tone has a lot of output and makes your amp distort more or more easily, ‘hot’ is the term that’s being used. Generally speaking, ‘hot’ pickups have a higher DC and a stronger magnet (ceramic, alnico 5 or alnico 8).
Icepick – A sharp tone with a lot of highs and upper mids that cut through the mix and sometimes can be even considered painful to the ear. If I recall, the term Icepick is shortened from ‘icepick through the head’, or similar.
Mushy/Muddy – When your tone has a lot of low end but lacks articulation, mushy or muddy is the term. The difference between the two is that muddy lacks even more clarity and mushy has even more emphasis on the low end.
Sizzle/fizz – If your tone simply don’t want to be clean up in the highs. If it’s just a little bit (which many players prefer), it’s called sizzle. If it’s a lot, it’s fizzy. It doesn’t mean that the tone has a lot of highs, just that it has a rough feel to the highs.
Twang – As the ‘quack’ is unique to the Strat, the twang is very unique to the Telecaster. If the quack has a scoop in the upper mids and a slight boost in the lows with softer highs, the twang has a scoop in the lower mids and a boost in the highs. The boost in highs can be experienced as an icepick in your ear, but this isn’t always the case. Twang isn’t just a lot of highs and upper mids, though. It also has a slight ‘nasal’ quality to it, that seems very hard to be reproduced in other guitars, just as the quack seems to be unique to the stratocaster.
Quack – A tone unique to the Stratocaster and happens only with the middle pickup engaged with either of the outer pickups. A quacky tone has a distinct scoop in the middle and has a voice reminiscent of a duck, hence the term quack.
Vintage – Vintage can refer to output (the opposite of hot) or tone. A vintage tone is often quite clean with a bump in the midrange and upper mids, lot of clarity, soft lows and sweet highs. Generally speaking, ‘vintage’ tones are achieved via pickups with less DC resistance and a magnet that isn’t as strong as an alnico 5, Alnico 8 or a ceramic.
Warm – A warm tone always has a lot of lows and lower mids. The term does not denote, however, the clarity of the tone. A warm tone can thus be very clear or muddy. Both are warm, just a different kind of warm.
Woofy / Boomy – Woofy and boomy are quite similar, but boomy is a bit tighter than woofy. Nevertheless, both have a lot of lows. It doesn’t mean that the lows aren’t tight (because usually, they are if one of these terms is being used), just that there’s a lot of it in an disproportionate way.

What other tone terms have you heard that you didn’t know the definition for?