1. The tilde character ("~", ASCII 126). Also called "squiggle", "sqiggle" (sic - pronounced /skig'l/), and "twaddle", but twiddle is the most common term.
2. A small and insignificant change to a program. Usually fixes one bug and generates several new ones (see also shotgun debugging).
3. To change something in a small way. Bits, for example, are often twiddled. Twiddling a switch or knob implies much less sense of purpose than toggling or tweaking it; see frobnicate. Bit twiddling connotes aimlessness, and at best doesn't specify what you're doing to the bit; to "toggle a bit" has a more specific meaning.
(31 Jan 1995)