messmate

A person with whom one eats regularly, as in a military mess.

An associate in a mess, especially in a ship’s mess; one who eats ordinarily at the same table with another.

In zoology, a commensal.

In botany, same as messmate-tree.

An associate in a mess.

an associate with whom one shares a mess (eating place) on a ship

(nautical) an associate with whom you share meals in the same mess (as on a ship)