Comment by shit_game
The best way I've come to describe glitch art in my papers or talks with peers is that a "glitch" in the context of glitch art is the deliberate abuse of a format of media, taking advantage of either noise, compression schemes, or undefined behavior to produce media that would otherwise not exist (due to contraints of, say, a compression algorithm and a binary format like JPEG), or to reproduce media that is discarded by these (and other) mechanisms of the format (The Ghost in the MP3[0] is a fantastic, and arguably the pioneering work in this regard).
Formats such as circuitbending are alien to me, as I primarily work with digital and occasionally analog photos and videos, but generally follow the same principles of breaking away from intended use of some set of rules to express illegal states.