Yes, open is playable
...and is worth 8 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Open" Definition
noun
A tournament or contest in which both professional and amateur players may participate.
An undisguised or unconcealed state: brought the problem out into the open.
An unobstructed area of land or water.
The outdoors: camping in the open.
open and unobstructed space as.
verb-intransitive
Games To make a bid, bet, or lead in starting a game of cards.
To be performed, shown, or made available to the public for the first time: The play opens next week.
To be priced or listed at a specified amount when trading begins: Shares opened high and fell sharply.
To become open: The door opened slowly.
To become receptive or understanding.
idiom
Open fire To begin firing on.
phrasal-verb
Open up Informal To accelerate. Used of a motor vehicle.
Open up Informal To speak freely and candidly: At last the frightened witness opened up and told the truth.
Open up To begin firing: The artillery opened up at dawn.
Open up To begin operation: The new store opens up next month.
Open up To make available or accessible: open up new markets.
verb
To move (as a door) from a closed position.
To make available for entry or passage by turning back (as a barrier) or removing (as a cover or an obstruction).
To make available for or active in a regular function .
To make accessible for a particular purpose .
To initiate access to (a computer file) prior to use.
We love the game of Scrabble®, which is why we created Free Scrabble Dictionary - a simple lookup tool to check if the word you want to play is valid in the game of Scrabble®. At the top of every page, you can enter your word and click "Search Dictionary." We'll let you know whether your word is playable and provide a few definitions as well.