Synonyms for Pro tem:

adj.

acting (adjective)
deputy, performing, alternate, functioning, working, temporary, practicing, operating, surrogate, acting.
all (adjective)
pro tempore.
temporary (adjective)
passing, impermanent, acting, short-lived, fleeting, provisional, substitute, alternate, interim, ad interim, brief, transient, pro tempore.

adv.

all (adverb)
pro tempore.

n.

fleeting, passing, brief, short-term, ad interim, floating, transient, interim, continue, provisional, short-lived, inconstant, substitute, variable. pro tem (noun)
pro tempore, temporary, impermanent.

Other synonyms:

interim, provisional, ad interim. Other relevant words:
impermanent, short-lived, provisional, interim, ad interim, brief, fleeting, substitute, pro tempore, passing, transient, short-term.