B1 or S1-xxx = (Basic)Series 1, 2, 3, 4, etc.
L1-6 = Legends 1, 2, 3, 4, 5, 6
BP1-xxx = Battle Pack 1, 2, 3, 4, etc.
DM = Defining Moments
EG = Entrance Greats
SCSA = Stone Cold Steve Austin
WHC = World Heavyweight Championship
Not really abbreviations, but every rookie should be on the look out for these references:
factory = means your custom/fix-up looks like it was factory-made by Mattel themselves
wrestlers with beards = usually means a heel turn
topless Mick Foley = don't ask
Stong = Sting's evil twin brother
Yamuna = fairly new reference out of SDCC 2013 referring to the Tamina figure, still don't know the whole story
flawlessly erected = our new Mission statement