Is punter a word in the Scrabble Dictionary

Yes, punter is playable

...and is worth 11 points.

Found in the following dictionaries

Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)

"Punter" Definition

noun

A customer of a commercial establishment, frequently of a pub or (alternatively) of a prostitute.
Source: Wiktionary
One who bets (punts) against the bank (banque).
Source: Wiktionary
One who gambles. See speculator.
Source: Wiktionary
One who oars or poles a punt (pontoon).
Source: Wiktionary
One who punts a football.
Source: Wiktionary