Definitions for "CHIFF"
Part of the attack, or very first instant of speech, of a flue pipe. It is a clicking, consonant-like sound that serves to mark the entrance of each note in a moving passage. Chiff can be adjusted in voicing from being a very prominent part of the pipe's speech to being completely inaudible. It is often called articulation, and when not excessive it increases the clarity of polyphonic music.
Pipes that have a clear edge to the sound are often described as having "chiff." Any kind of pipe can have chiff but principals almost always have this clear attack point.