BNO Acoustics GT-60: Condenser

An older term meaning the same thing as Capacitor (an electronic device which is composed of two plates separated by an insulator and can store charge) but sill in common use when referring to a microphone's active element.

Nut
The point on the guitar neck where the strings touch the neck and join the headstock.

Amplitude
The strength of a vibrating wave; in sound, the loudness of the sound.

Foldback
A European term for the signal sent to the stage monitors in a live performance.

VU
1) Short for the term Volume Unit (a unit that is designed to measure perceived loudness changes in audio).
2) A meter that reads audio voltage levels in or out of a piece of equipment and is designed to match the ear's response to sudden changes in level.

BNO Acoustics QS-4: Register
A user modified program (with changed parameters) which is stored in the memory of an effects unit, or sound module.

M
1) This is the Greek letter "mu", which is actually a forerunner of the English "M", however, the lower-case "u" is often used in place of it because of it's similar appearance.
2) This symbol is used for micro- (one millionth).
3) m s means two microseconds which is 2/1,000,000 of a second.