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Once a year, AAA (American Automobile Association) arrives unannounced and evaluates hotels from a guest's perspective.

Hi,

Does "arrives unannounced" in the above mean "arrives without announcing or notifying hotels in advance?" Thanks.
Comments  
Unannounced (adjective)
Happening without anyone being told or warned in advance 

AAA arrives unannounced means that AAA arrives without anyone being told or notified.

Another example:
He just showed up unannounced on my doorstep. ( He came without telling me before )
Thanks, YoungBuddy.

Is it right and idiomatic to say "he was an unanounced visitor" or " ... a visitor unanounced?"

He just showed up unannounced on my doorstep. ( He came without telling me before )
Students: We have free audio pronunciation exercises.
I think it's common, I once read an article on the internet titled
" Unannounced visitors ! Do you open your door ? "
But i don't know if it's an idiom or not ... so let's wait for a native speaker and see Emotion: wink