I am NOT looking for the term as it applies to the facilities on a cruise ship or other passenger vessel, nor on a military vessel of any stripe. Rather I want the right term for the freight ship.
Am I correct that it would be mess, mess room, or mess hall, and NOT galley? The latter, I understand it, is specifically the kitchen. No?
For the unlicienced crew sorry but a brain fart I can not come up with it.
For the Officers it was the Officer’s Solon.
tomndeb was a merchant sailor, he’ll know. Those of us in the navy ate on the mess deck.
I thought you ate in the crew’s mess, which happened to be located on the mess deck. 
Naval officers eat in the wardroom. The food is cooked in the galley.
If the dining room is on the mess deck, what is on the poop deck?
(No…seriously)
Just the dining room. Many modern merchant vessels don’t even split officers from crew nowadays.
Merchant seaman chirping in here, the crew (below officer rank) eat in the crew mess. Whilst the Officers eat in the saloon. However the company I work for is rather old fashioned and I imagine with small crews on most merchant ships that seperating the crew is becoming less common. Basically it will depend on the company, ship size and design of the ship.
The [poop deck](poop deck) is the deck that forms the roof of the rearmost cabin on a sailing vessel.
A ship is pooped when a sea breaks over the after deck. I don’t know which term came first.