ACL = Austin City Limits
AV = American Vintage, as in AV52RI, for a '52 Telecaster reissue)
BF = Black face (Fender amp with black control plate, often used as a prefix to amp acronyms)
BJ = Fender Blues Jr. amp
BSB = Butterscotch Blonde
BWB = Black/White/Black layered pickguard
Cap = Capacitor
CAR = Candy Apple Red
CIC = Crafted in China
CIJ = Crafted in Japan (Fender Japan guitars after 1996/7)
CS = (Fender) Custom Shop
CTS = Maker of potentiometers used in guitars
DR = Fender Deluxe Reverb amp
DRRI = A reissue of the '65 Fender Deluxe Reverb amp
EH = Electro-Harmonix, maker of effect pedals
EV = Electro Voice speaker
EQ = Equalizer
FX = Effects (as in FX pedals)
GAS = Guitar/Gear Acquisition Syndrome
GC = Guitar Center
GFS = Pickups and/or other parts made by/for guitarfetish.com
HB = Humbucking guitar/bass pickup
HC = Harmony Central (another forum, not affiliated)
HRD/HRDx = Fender Hot Rod Deluxe amp
HRDv = Fender Hot Rod DeVille amp
HSS = Humbucker/single coil/single coil pickup configuration
HV = High voltage
HW1 = Fender Highway One Telecaster (or other instrument)
IMO/IMHO = In My Opinion/In My Humble Opinion
J = Fender Jazz Bass
LP = Gibson Les Paul
LPB = Lake Placid Blue
MB = Fender Musicmaster Bass amp
MF = Musician's Friend
MIA = Made in America (USA)
MIC = Made in China
MII = Made in Indonesia / Made in India
MIJ = Made in Japan (Fender Japan guitars up until 1996/7)
MIK = Made in South Korea
MIM = Made in Mexico
MIT = Made in Taiwan
MMB = Fender Musicmaster Bass amp
MOP = Mother of Pearl
MOTS = Mother of Toilet Seat (plastic imitation of MOP, or similar)
NOS = New Old Stock
NTTAWWT = "Not that there's anything wrong with that" (see: Seinfeld)
OD = Overdrive
OT = Output transformer
OV = (Fender) Original Vintage (guitar pickups)
P = Fender Precision Bass
PCB = Printed circuit board
PJ = Fender Pro Junior amp
P/J = Precison + Jazz bass pickup configuration
Pot = Potentiometer
PR = Fender Princeton Reverb amp
PRRI = A reissue of the '65 Fender Princeton Reverb amp
PU = guitar/bass pickup
P/U = guitar/bass pickup
Pup = guitar/bass pickup
PT = Power transformer
PV = Peavey
RI = Reissue (often added to amp acronym, eg DRRI)
SC = Single coil guitar/bass pickup, or Fender Super Champ amp
SCXD = Fender Super Champ XD amp
SD = Seymour Duncan (maker of guitar pickups)
SER = Series
SF = Silver face (Fender amp with silver control plate, often used as a prefix to amp acronyms)
SMD = Surface-mount devices (on circuit boards)
SR = Fender Super Reverb amp
SS = Solid state
STD = Standard
TR = Fender Twin Reverb amp
TRRI = A reissue of the '65 Fender Twin Reverb amp
TS-9/TS-808 = Classic Ibanez Tube Screamer OD pedals
TTIUWP = This Thread Is Useless Without Pictures!
WBW = White/Black/White layered pickguard
YMMV = Your Mileage May Vary
12AX7 = Pre amp tube, used in most amps
5E3 = Fender Tweed Deluxe model amp
5E5-A = Fender Tweed Pro model amp
5E7 = Fender Tweed Bandmaster model amp
5E8-A = Fender Tweed Twin model amp
5F1 = Fender Tweed Champ model amp
5F4 = Fender Tweed Super model amp
5F6-A = Fender Tweed Bassman model amp
6L6 = Power tube, used in high-wattage Fender amps (Twin, Super, Showman...)
6V6 = Power tube, used in low-wattage Fender amps (Champ, Princeton...)