I did turn up a number of nice world music glossaries, which will get a post of their own soon.
Drummer Café - music and drumming terms
Very good, though not comprehensive, and could a little bit of a polish with an editor. Original, practical rather than scholarly definitions. Deals with common advanced drumming terms, which users are most likely to need help understanding, not so much with basic things.
half-time feel Playing any groove twice as slow as the regular feel, while the measures of music continue as normal. To achieve this, in 4/4 time for example, the back-beat would play on beat 3, rather than the normal fashion ... playing on beats 2 and 4.
This terms is used in relation to the pulse of the music, which, 99% of the time, is the quarter-note.
ostinato A musical phrase repeated over and over during a composition.
An ostinato on the drums would be a rhythmic pattern played over and over again. One approach might be to play a single pattern over and over again with the feet, while the hands solo over the top. Another example might be to establish a groove on the drumkit, while one limb improvises around the drums. When an ostinato is used within a solo, it typically takes on the role of accompaniment ... allowing the performer to play over the top of this regularly, reoccurring pattern.
Ostinato drumming is nothing new; listen to Max Roach solo drum compositions. Terry Bozzio gained a lot of notoriety using ostinatos in his solo performances because of the massive set-ups he uses. There are countless drummers who use ostinato patterns in their playing. If we take the actual definition of the term ostinato ... we quickly realize that drummers, especially those from the Jazz genre, have been using ostinatos for over seven decades.Drumbook - drum glossary
Nice middle-school level glossary; definitions are short and clear, though not necessarily complete. Includes some basic, colorful terms like "burn" and "four on the floor."
Comp Comping means to play rhythmic motifs on the drums that accompany and complement a jazz soloist. It also refers to the chords played by a guitar or piano to accompany a soloist.
Swing A rhythmic style where notes off the beat are played shorter than notes on the beat. Eighth notes and sixteenth notes that fall on the off beat are played on the last triplet subdivision. The swing feel does not necessarily have to be triplets. The swing ratio can vary between 1:4 and 1:1.
Swing can also refer to a style of big band jazz music from the 1920s and 30s swing era.
When a jazz band rhythmically locks in together in a way that feels good the music is said to swing.
Time signature The time signature specifies how many beats in each bar. It is written at the beginning of a piece if music and anywhere that the time signature changes. The top number indicates the number if beats in the bar and the bottom number indicates the length of each beat. For example 4/4 means four quarter notes to each bar. 6/8 means six eighth notes to each bar. 4/4 is the most common time signature.
Formédia - latin rhythms glossary
Great, concise introduction to terms pertaining to Latin-American (mainly Afro-Cuban) music and drumming. Site includes examples of types of clave, bell patterns, and (actually usable) patterns for drum set. Great, I'd just like to see more detail and more entries!
Cascara The Spanish word for shell and a rhythmic pattern, played on the side of the timbale. The cascara is played in salsa during verses and softer sections of the music.
Clave A spanish word meaning key, the clave is serving as a skeletal rhythmic figure around which the different drums and percussion are played. The rhythm is often played with two wooden sticks called the claves. Whether played or not, it is implied throughout the music.
Mambo Most commonly referred to as a repeating section of a song, also known as montuno. It is often mistaken for a specific type rhythm or song form. The dance done during this part of the music also became known as the mambo.Columbia University Center for Jazz Studies - jazz glossary
Excellent glossary of general jazz terms. Definitions are very brief, but good for giving newer jazz students a sense of the terrain.
back beat A rhythmic device in which the second and fourth beat of a measure is heavily emphasized in 4/4 time.
double-time A doubling of tempo in the melody while the accompanying instruments remain at the slower tempo; or all the instruments doubling the tempo together. This is a common rhythm device in ballad playing.
groove A repeated pattern in the rhythm section most common in funk playing; a repeated rhythm pattern that creates the dominant feel of a piece.
A Passion For Jazz - glossary of jazz terms
Very nice; concise but complete definitions, mostly general jazz terms. Much specifically for melodic instruments, not so much specifically for the drums. Read it on the author's site.
Broken time: A way of playing in which the beat is not stated explicitly. Irregular, improvised syncopation. Especially applied to bass and drum playing.
Chart: (1) Any musical score. (2) A special type of score, used by Jazz musicians. Only the melody line, words (if any) and chord symbols are given. Clef, key signature and meter are given once only, at the beginning. The standards of musical notation and calligraphy are low. Details are often scanty or inaccurate, which encourages the musician to amend and elaborate the chart for his own purposes. Every Jazz musician has his own book of miscellaneous charts.
Swing: (1) The style of the 30s, when the big band was the dominant form of Jazz. The style implies certain types of harmony (use of added 6ths rather than 7ths in major and minor chords, of un-embellished diminished chords, frequent use of the augmented 5th and little use of the augmented 11th, etc.) and a rhythmic organization that states the beat explicitly, puts more weight on 1 and 3 and tends to obey the bar-line phrasing. (2) A rhythmic manner, unique to Jazz, in which the first of a pair of written 8th notes is played longer than the second, even twice as long, while the second tends to receive a slight accent, though the distribution of accents is irregular and syncopated. (The degree of this effect depends on the overall tempo, and is modified by the requirements of expression and phrasing.) (3) As a direction in a chart, played with a swing feel, as opposed to latin. (4) A mysterious, unexplainable quality in any music, but especially Jazz, which makes one 'feel that shit all up in your body' (Miles Davis).
Syncopation: The process of displacing 'expected' beats by anticipation or delay of one-half a beat. The natural melodic accent which would fall, in 'square' music, on the beat, is thus heard on the off-beat. This adds a flavor of ambiguity as to where the beat is (not an actual ambiguity, only a flavor).
Wikipedia - Glossary of jazz and popular music terms
Long but spotty, much of it pertaining to sound engineering and gigging in the rock world. Not useless, but kind of marginal.
bouncer (or "doorman" or "cooler"): a security staffer who works at music and concert venues such as bars and clubs; the job of a doorman is to check for age of majority ID; search for concealed weapons, drugs, or alcohol; remove intoxicated or aggressive patrons; and enforce the rules of the venue (e.g., a rule against stage-diving or moshing).
syncopation: a disturbance or interruption of the regular flow of rhythm.
woodshed: a slang term which refers to an intense period of practice and self-development that a musician has (or is believed to have) undergone. If a musician has dramatically improved his or her technique in a short period, a critic may state that the performer has "woodshedded" on technique.
Drum Bum - drums glossary
I'm not wild about this one at all. Drumbum.com is a site of drumming-related merchandise and novelties, and apparently the informational content was an afterthought. Definitions are very short, often incomplete, inadequately descriptive, and/or misleading. Reproduced on a number of other robo-sites. Close to worthless.
acoustic drums - drums that are void of electronic components. Usually made of wood or synthetic material only. And electronic drums are void of acoustic drums.
permutation - a term popularized in drumming over the last 10 years. It refers to beat displacement where all beats will move forward say, one eighth note. This method will create numerous variations of rhythmic possibilities.
rhythm - the manipulation of strong and weak beats, creating a flowing and/or syncopated pulse.
syncopation - when a beat or a musical phrase is syncopated.