This is the 1413th most frequent Arabic word.
زار
"زار" means "to visit."
The verb 'زار' here means 'visited', indicating that someone went to a place (the museum) to see and learn about it.
زار أحمد المتحف الوطني البارحة.
Ahmed visited the national museum yesterday.
In this question, 'زار' is used in the interrogative form to ask if someone visited a specific person (the dentist).
هل زرت طبيب الأسنان الأسبوع الماضي؟
Did you visit the dentist last week?
'زائر' (visitor) is a derivative of 'زار', describing a person who visits a place.