πλάξ, -ακός, ἡ [in LXX for לוּחַ ;] anything flat and broad. __1. a plain (poët.). __2. In late writers (Luc., al.), a flat stone, a tablet: Refs 2Co.3:3, Heb.9:4.† (AS)
Thayer:
1) a flat thing, broad tablet, plane, level surface (as of the sea)
πλάξ
plax
plax
From G4111; a mouldingboard, that is, flat surface (“plate”, or tablet, literally or figuratively)
πλάσσω
plassō
plas'-so
A primary verb; to mould, that is, shape or fabricate
KJV Usage: form.
G1542 ἑκατονταπλασίωνἑκατονταπλασίων
hekatontaplasiōn
hek-at-on-ta-plah-see'-own
From G1540 and a presumed derivative of G4111; a hundredtimes
KJV Usage: hundredfold.
G4110 πλάσμαπλάσμα
plasma
plas'-mah
From G4111; something moulded
KJV Usage: thing formed.
G4112 πλαστόςπλαστός
plastos
plas-tos'
From G4111; moulded, that is, (by implication) artificial or (figuratively) fictitious (false)
KJV Usage: feigned.
G4116 πλατύςπλατύς
platus
plat-oos'
From G4111; spread out “flat” (“plot”), that is, broad
KJV Usage: wide.
G4141 πλήσσωπλήσσω
plēssō
place'-so
Apparently another form of G4111 (through the idea of flattening out); to pound, that is, (figuratively) to inflict with (calamity)