1.  internationalist(n = noun.person) - an advocate of internationalism;
is a kind of advocate, advocator, exponent, proponent
Derived form noun internationalism₁

2.  internationalist(n = noun.person) - a member of a socialist or communist international;
is a kind of socialist
is a member of international

   internationalist(s = adj.all) internationalistic - influenced by or advocating internationalism;

1.  One who is versed in the principles of international law. [1913 Webster]

2.  A member of the International; one who believes in, or advocates the doctrines of, the International. [1913 Webster]