ORIENTEE, a word or not in Scrabble?

I am confused why I cannot use 'ORIENTEE' as a word in Scrabble.

It should mean 'someone who is attending orientation, as in a new employee (and the word is formed analogously: 'someone being oriented'.

Google says 'orientee' is not an acceptable word in the English dictionary. I have encountered this word quite a lot in the hospital for so many years.

So, is it a word or not, in real life or in Scrabble?

Allnurses.com, a US nursing website, says in one thread

I was writing a paper for a class in my BSN program and typed in orientee and the spellcheck said it wasn't a word, and I went to dictionary.com and same thing. I've always used that word for a person on orientation. So if it's not a word what should I use in my paper - right now I'm going to put "new hire" or "newly hired employee" but am open to suggestions.

I've always used orientee also. I'm not sure if it would matter for your paper or not, whether "orientee" is in the dictionary. I think a lot of medical lingo wouldn't be found there, even though they're accepted words within the profession.

So although its meaning "one who is being oriented" is fairly obvious as the -ee suffix is productive, it's jargon within the US medical sector.

Because it's jargon and formed from a productive suffix, it's entirely possible that smaller or less comprehensive or specialised dictionaries wouldn't list it. It's not listed in OED either, nor in Oxford's specialist medical dictionaries.

As regards Scrabble, valid words are strictly defined in whichever dictionary you're using for your game. If it's not there, it's not valid.

The official scrabble rules state:

Before the game begins, all players should agree upon the dictionary that they will use, in case of a challenge. All words labeled as a part of speech (including those listed of foreign origin, and as archaic, obsolete, colloquial, slang, etc.) are permitted with the exception of the following: words always capitalized, abbreviations, prefixes and suffixes standing alone, words requiring a hyphen or an apostrophe.

If you agreed on a dictionary before you started playing, then you should consult the chosen dictionary.

If you didn't, you should make a point of agreeing on a dictionary before the next game starts.