The Ultimate Acronym List:
General:
GB: gymnastics bodies
GST: Gymnastic Strength Training™
BtGB: building the gymnastics body; Coach's book.
MAG:
XR: Xtreme rings or still rings.
PB: parallel bars
FX: floor exercise
PH: pommel horse
VT: vault
HB: high bar
MAG: men's artistic gymnastics (Coach Sommer's sport).
Courses:
F: Foundation
F1: Foundation 1, the first volume of progressions.
F2,F3,F4: the other three volumes
F7: doing all 7 foundation exercises in a single workout
F3/F4: splitting the foundation workout and doing 3 exercises one day then the remaining 4 another day.
H: handstand series
H1: freestanding handstand course
H2: press handstand course
H3: one-arm handstand course
M: movement
R: Rings
R1: Rings volume 1
H: Hungarian
Foundation general terms:
PE: preparatory exercise
SE: specific exercise
iM: integrated mobility exercise
FL: Front lever
sPL: straddle planche
SL: side lever
MN: manna
SLS: single leg squat
HBP: Hollow-back press (aka bowers)
RC: rope climb
Exercise acronyms: (credit to Adara9 for collecting all of these)
Adara9 has put together a list of all the names and acronyms of exercises in F1.