There are a lot of fountain pen terms thrown around on various forums and blogs. To save time, many times these popular terms are abbreviated, so here’s a guide to help you out!

A4 8.25″ x 11.75″ Paper size
A5 5.75″ x 8.25″ Paper size
Aero Aerometric filler
B Broad
BB Double broad, or Blue Black
BBB Triple broad
BBK Noodler’s Bad Belted Kingfisher
BP Ballpoint pen
BSB Noodler’s Baystate Blue
C Course
C/C Cartridge/Converter
Cart Cartridge
CdA Caran d’Ache
ED Eyedropper
EF/XF Extra Fine
Estie Esterbrook
G/GSM Grams per Square Meter (paper weight)
F Fine
FM/MF Fine Medium
FP Fountain Pen
FPN Fountain Pen Network
FS For Sale
ID Ink Drop
IMHO In My Humble Opinion
IPG Iridium Point Germany
L2K Lamy 2000
LE Limited Edition
M Medium
MB Mont-Blanc
MP Mechanical Pencil
MS Music
Newbie/Noob Fountain pen novice
NIB New In Box
NM Nevermind
NOS New Old Stock
OB Oblique Broad
OBB Oblique Double Broad
OM Oblique Medium
OP Original Poster
P51 Parker 51
Pel Pelikan
PO Posting
PR Private Reserve
R&K/RnK Rohrer and Klingner
RB/RP Rollerball Pen
ROTFL Rolling On The Floor Laughing
SF Soft Fine
SITB Stuff/slime/sludge In The Bottle
SM Soft Medium
SU Signature (stub)
Vac Vacumatic filler
VP Pilot Vanishing Point
WM Waterman
WTB Want To Buy
WTS Want To Sell
WTT Want To Trade
XXF Super Extra Fine
XXXF Needlepoint
YMMV Your Mileage May Vary
YOL Yard-O-Led
Z Zoom (multi-angled) nib