The Pentrace Guide to Acronyms & Initialisms
Every now & then someone asks for help understanding the acronyms & initialisms they see here and elsewhere around the Net, so I put this together.

If anyone would like to contribute additional acronyms (especially the pen-specific ones) -- or to correct any errors I may have made, for that matter -- I'll maintain the list. -- Linda B.

A general guide to acronyms can be found at the Acronym Finder page

 
ALL-PURPOSE ACRONYMS:
These acronyms are in general use in the wired world. Most originate in the world of IRC (Internet Relay Chat) chat rooms.

BEG: -- Big Evil Grin
BFTB or BFYB: -- Bang For The [or Your] Buck
BTW: -- By The Way...
FWIW: -- For What It's Worth
G: -- Grin
IIRC: -- If I Remember [or Recall] Correctly
IMHO: -- In My Humble Opinion
IMNSHO: -- In My Not So Humble Opinion
IMNTBHO: -- In My Never To Be Humble Opinion
IMVHO: -- In My Very Humble Opinion
IMO: -- In My Opinion
LOL: -- Laughing Out Loud
RO[T]FL: -- Rolling On [The] Floor Laughing
RO[T]FLMAO: -- Rolling On [The] Floor Laughing My A$$ Off
RO[T]FLMBO: -- Rolling On [The] Floor Laughing My Butt Off
RO[T]FLMAOAPMP: -- Rolling On [The] Floor Laughing My A$$ Off And Peeing My Pants
RO[T]FLMAOASTC: -- Rolling On [The] Floor Laughing My A$$ Off And Scaring The Cat
TTFN: -- Ta-ta For Now
TTYL: -- Talk To You Later
VBG: -- Very Big Grin
VBEG: -- Very Big Evil Grin
VVBG: -- Very Very Big Grin
YMMV: -- Your Mileage May Vary (i.e., your results/opinion may differ)
 
PEN-SPECIFIC ACRONYMS:
These acronyms are specific to the pen world. Some collectors or dealers may use slight variations on these.
BCHR: -- Black Chased Hard Rubber
BHR: -- Black Hard Rubber
BF: -- Button Filler
BP: -- Ballpoint
C/C: -- Cartridge/Converter [fill method]
CF or C/F: -- Cartridge Filler
CS or C/S: -- Conway Stewart
ED: -- Eye-Dropper
EX: -- Excellent (condition)
FPH: -- Fountain Pen Hospital
FPOTW: -- Fountain Pens Of The World [book by Andreas Lambrou]
GF: -- Gold-Filled
GP: -- Gold Plate[d]
LE: -- Limited Edition
LF: -- Lever-Fill[ed]
MB: -- Mont Blanc
MIB: -- Mint In Box [condition - i.e., all original; never dipped or filled]
MP: -- Mechanical Pencil
NM: -- Near Mint [condition]
NMIB: -- Near Mint In Box
NOS: -- New Old Stock
OS or O/S: -- Oversize [i.e., extra large/long]
PF: -- Piston-Fill[er]
PFM: -- [Sheaffer's] Pen For Men
RB: -- Roller Ball
RCHR: -- Red Chased Hard Rubber
RHR: -- Red Hard Rubber
RG: -- Rolled Gold
SS or S/S: -- Sterling Silver
 
NIBS:
These acronyms are used to describe nibs. Some collectors, manufacturers or dealers may use slight variations on these.
B: -- Broad
BB: -- Double-Broad
BBB: -- Triple-Broad
EF: -- Extra-Fine
F: -- Fine
I: -- Italic
LO: -- Left Oblique [i.e., for left-handed writer]
M: -- Medium
OB: -- Oblique Broad
OBB: -- Oblique Double-Broad
OF: -- Oblique Fine
OM: -- Oblique Medium
RO: -- Reverse Oblique (aka Left Oblique)
S: -- Stub
S/F: -- Semi-Flex[ible]
XF: -- Extra-Fine